Measurement Unit Glossary

Meter m also: meter, metre, meters

The meter is the SI base unit of length, defined since 1983 as the distance light travels in a vacuum in 1/299,792,458 of a second. Every other length unit on this site is defined in terms of it.

Used in: architectural drawings and building codes outside the US; athletics track and field events; scientific measurement.

Kilometer km also: kilometre, kilometers, kilometres

The kilometer is 1,000 meters, the standard unit for road distances, maps, and geography in most of the world. Road signs, running races, and vehicle odometers outside the US and UK all use it.

Used in: road distances and signage outside the US; running and cycling race distances; flight and shipping routes.

Centimeter cm also: centimetre, centimeters, centimetres

The centimeter is one hundredth of a meter (10 millimeters). It is the everyday small-length unit in metric countries, used where inches would be used in the US.

Used in: body height and clothing measurements; furniture and interior dimensions; school rulers and technical sketches.

Millimeter mm also: millimetre, millimeters, millimetres

The millimeter is one thousandth of a meter. Engineering and manufacturing drawings in metric countries are dimensioned almost exclusively in millimeters to avoid decimal points.

Used in: engineering and CAD drawings; manufacturing tolerances; rainfall measurement.

Micrometer um also: micron, micrometers, microns

The micrometer (micron) is one millionth of a meter, or a thousandth of a millimeter. It is the working scale of cell biology, semiconductor features, and surface-finish specifications.

Used in: microscopy and cell biology; semiconductor manufacturing; surface roughness specifications.

Nanometer nm also: nanometre, nanometers, nanometres

The nanometer is one billionth of a meter. Wavelengths of visible light (380–700 nm) and modern chip process nodes are quoted in nanometers.

Used in: light wavelengths and optics; chip fabrication process nodes; nanotechnology research.

Mile mi also: miles

The mile is defined as exactly 1,609.344 meters (5,280 feet) under the 1959 international yard and pound agreement. It remains the road-distance unit of the US and UK.

Used in: US and UK road distances and speed limits; marathon and running pace calculations; aviation and shipping in US usage.

Yard yd also: yards

The yard is defined as exactly 0.9144 meters by the 1959 international agreement; the foot and inch derive from it. It survives mainly in sport and US fabric and landscaping trade.

Used in: American football field positions; fabric and textile sales in the US; golf course distances.

Foot ft also: feet, foot

The foot is defined as exactly 0.3048 meters (12 inches) under the 1959 international yard and pound agreement. US construction, real estate, and aviation altitude all run on feet.

Used in: US construction and real estate floor plans; aviation altitude worldwide; human height in the US and UK.

Inch in also: inches, "

The inch is defined as exactly 25.4 millimeters, one twelfth of a foot. Screen sizes, pipe diameters, and US manufacturing drawings are specified in inches.

Used in: screen and display sizes; US manufacturing and plumbing specifications; paper and photo print formats.

Nautical Mile nmi also: nautical miles

The nautical mile is defined as exactly 1,852 meters, originally one minute of latitude along a meridian. Marine and air navigation use it because it maps directly onto chart coordinates.

Used in: marine navigation and charts; aviation flight planning; territorial water boundaries.

Convert length units →

Kilogram kg also: kilograms, kilo, kilos

The kilogram is the SI base unit of mass, defined since 2019 by fixing the Planck constant rather than by the old platinum-iridium prototype. It is the reference for every other mass unit on this site.

Used in: body weight outside the US; groceries and food packaging worldwide; freight and laboratory work.

Gram g also: grams, gramme, grammes

The gram is one thousandth of a kilogram. Recipes, nutrition labels, and postal scales work in grams because the kilogram is too coarse for them.

Used in: cooking and baking recipes; nutrition labels; letter postage and jewelry.

Milligram mg also: milligrams, milligramme, milligrammes

The milligram is one thousandth of a gram, or a millionth of a kilogram. Medication dosages and trace nutrient amounts are stated in milligrams.

Used in: medication dosages; vitamin and supplement labels; analytical chemistry.

Microgram ug also: micrograms, mcg

The microgram is one millionth of a gram. It appears on supplement labels (often as mcg or µg) for vitamins like B12 and D, and in toxicology and air-quality limits.

Used in: vitamin labels (mcg); air quality limits; toxicology thresholds.

Metric Ton t also: tonne, tonnes, metric tons

The metric ton (tonne) is exactly 1,000 kilograms. Freight, agriculture, and industry quote bulk quantities in tonnes, and it differs from both the US and imperial ton.

Used in: shipping freight and cargo; agricultural yields; industrial raw materials.

Pound lb also: pounds, lbs

The pound (avoirdupois) is defined as exactly 0.45359237 kilograms under the 1959 international agreement. Body weight, groceries, and shipping in the US run on pounds.

Used in: body weight in the US; US grocery and butcher pricing; gym weight plates and fitness tracking.

Ounce oz also: ounces

The ounce is one sixteenth of a pound, exactly 28.349523125 grams. US recipes, portion sizes, and postal rates use it for quantities a pound would state too coarsely.

Used in: US recipe ingredients; food portion sizes; US postal rates.

Stone st also: stones

The stone equals 14 pounds, exactly 6.35029318 kilograms. It survives almost exclusively for stating body weight in the UK and Ireland.

Used in: body weight in the UK and Ireland; boxing and horse racing weight classes.

US Ton ton also: short ton, us tons

The US (short) ton is 2,000 pounds, exactly 907.18474 kilograms. American freight, mining, and vehicle ratings use it, and it is about 10% lighter than the metric tonne.

Used in: US truck and freight capacity; US mining and aggregate sales; vehicle towing ratings.

Imperial Ton long-ton also: long ton, uk ton, imperial tons

The imperial (long) ton is 2,240 pounds, exactly 1,016.0469088 kilograms — slightly heavier than the metric tonne. It persists in British maritime usage and ship displacement figures.

Used in: ship displacement figures; historical British engineering documents.

Convert mass units →

Celsius C also: celsius, centigrade, °C

The degree Celsius is the SI temperature unit for everyday use, with 0 °C at the freezing point and 100 °C at the boiling point of water at standard pressure. It is offset from the kelvin by exactly 273.15.

Used in: weather forecasts outside the US; cooking and oven settings in metric countries; medical and laboratory temperatures.

Fahrenheit F also: fahrenheit, °F

The degree Fahrenheit sets water's freezing point at 32 °F and boiling point at 212 °F, dividing the interval into 180 degrees. The US uses it for weather, cooking, and medicine.

Used in: US weather forecasts and thermostats; US oven and recipe temperatures; body temperature in the US.

Kelvin K also: kelvin, °K

The kelvin is the SI base unit of thermodynamic temperature, defined since 2019 by fixing the Boltzmann constant. Its zero point is absolute zero, and one kelvin equals one degree Celsius in size.

Used in: physics and chemistry calculations; color temperature of lighting and displays; cryogenics and space science.

Rankine R also: rankine, °R

The degree Rankine is an absolute temperature scale using Fahrenheit-sized degrees, with 0 °R at absolute zero. US thermodynamics and aerospace engineering use it where absolute values are required in Fahrenheit units.

Used in: US thermodynamic engineering; aerospace and turbine calculations.

Convert temperature units →

Square Meter m2 also: square meters, sq m, sqm

The square meter is the SI derived unit of area — the area of a square one meter on each side. Apartment listings, building plans, and material quantities use it in metric countries.

Used in: apartment and house listings outside the US; flooring and paint coverage; building regulations.

Square Kilometer km2 also: square kilometers, sq km, km²

The square kilometer is one million square meters. Geography uses it for cities, lakes, parks, and countries — anything too large for hectares.

Used in: city and country land areas; national parks and nature reserves; population density figures.

Square Centimeter cm2 also: square centimeters, sq cm, cm²

The square centimeter is one ten-thousandth of a square meter. It suits small surfaces: paper, screens, wounds in medicine, and cross-sections in engineering.

Used in: medical wound and skin measurements; cross-sectional areas in engineering; stationery and packaging.

Square Millimeter mm2 also: square millimeters, sq mm, mm²

The square millimeter is one millionth of a square meter. Electrical wire cross-sections are its best-known use — cable sizes worldwide are specified in mm².

Used in: electrical cable cross-sections; precision mechanical parts; material stress calculations.

Hectare ha also: hectares

The hectare is 10,000 square meters — a square 100 meters on each side. It is the standard metric unit for land: farms, forests, and development sites.

Used in: farm and agricultural land; forestry management; real estate development parcels.

Acre acre also: acres

The acre is 43,560 square feet, exactly 4,046.8564224 square meters — historically the area a yoke of oxen could plow in a day. US and UK land sales still quote it.

Used in: US and UK land sales; farm and ranch sizes in the US; golf courses and estates.

Square Mile mi2 also: square miles, sq mi, mi²

The square mile is 640 acres, about 2.59 square kilometers. US geography uses it for counties, cities, and large land areas.

Used in: US city and county areas; US population density figures; large ranch and wilderness areas.

Square Yard yd2 also: square yards, sq yd, yd²

The square yard is exactly 0.83612736 square meters (9 square feet). US carpet, fabric, and concrete trades still price by the square yard.

Used in: carpet and flooring sales in the US; concrete pours; fabric quantities.

Square Foot ft2 also: square feet, sq ft, ft²

The square foot is exactly 0.09290304 square meters. It is the standard unit of US and UK real estate — home sizes, office leases, and rents are quoted per square foot.

Used in: US home and office sizes; commercial lease rates; construction material estimates.

Square Inch in2 also: square inches, sq in, in²

The square inch is exactly 6.4516 square centimeters. Pressure ratings (psi), screen areas, and small US manufacturing specs use it.

Used in: pressure specifications (pounds per square inch); small part manufacturing in the US; pizza and screen size comparisons.

Convert area units →

Liter l also: liters, litre, litres

The liter is exactly one cubic decimeter — a cube 10 cm on each side. Beverages, fuel, and engine displacement are sold and specified in liters across the metric world.

Used in: beverage bottles and cartons; fuel sales outside the US; engine displacement.

Milliliter ml also: milliliters, millilitre, millilitres

The milliliter is one thousandth of a liter, identical to one cubic centimeter. Medicine doses, cosmetics, and recipe liquids are measured in milliliters.

Used in: liquid medicine doses; cosmetics and toiletries; metric recipe liquids.

Cubic Meter m3 also: cubic meters, m³

The cubic meter is the SI derived unit of volume — 1,000 liters. Construction (concrete, excavation), water utilities, and freight all bill by the cubic meter.

Used in: concrete and excavation quantities; household water billing; shipping container capacity.

Cubic Centimeter cm3 also: cubic centimeters, cc, cm³

The cubic centimeter equals exactly one milliliter. Engine sizes (cc), medical syringes, and solid part volumes use it.

Used in: motorcycle and small engine sizes (cc); syringe volumes; solid object volumes in engineering.

Cubic Millimeter mm3 also: cubic millimeters, mm³

The cubic millimeter is one thousandth of a cubic centimeter. It appears in precision engineering, 3D printing material estimates, and medical imaging measurements.

Used in: 3D printing material volumes; medical imaging lesion sizes; precision part specifications.

US Gallon gal also: gallons, us gallons

The US gallon is defined as 231 cubic inches, exactly 3.785411784 liters. US fuel prices, milk jugs, and paint cans are all per-gallon quantities.

Used in: US fuel prices; US milk and beverage containers; paint coverage in the US.

US Quart qt also: quarts, us quarts

The US quart is a quarter of a US gallon, about 0.946 liters. US motor oil, ice cream, and canning recipes are sold and written in quarts.

Used in: US motor oil containers; US canning and cooking.

US Pint pt also: pints, us pints

The US pint is half a US quart, about 473 milliliters — noticeably smaller than the 568 ml imperial pint. US ice cream, berries, and draft beer are sold by the pint.

Used in: US ice cream and berry containers; US draft beer servings.

US Cup cup also: cups, us cups

The US cup is 8 US fluid ounces, about 236.6 milliliters. It is the backbone of American recipe measurement for both liquids and dry ingredients.

Used in: American recipe measurements; coffee maker capacities.

US Fluid Ounce fl-oz also: fluid ounces, fl oz, us fl oz

The US fluid ounce is about 29.574 milliliters, one eighth of a US cup. Beverage cans, cosmetics, and baby formula in the US are labeled in fluid ounces.

Used in: US beverage can and bottle sizes; cosmetics labeling in the US; baby formula preparation.

Tablespoon tbsp also: tablespoons, tbs

The tablespoon is three teaspoons, about 14.79 milliliters in US recipe measure. Cooking and nutrition labels use it for oils, sauces, and medicine in the US.

Used in: recipe oil and sauce quantities; nutrition serving sizes.

Teaspoon tsp also: teaspoons

The teaspoon is about 4.93 milliliters in US recipe measure, one third of a tablespoon. Baking ingredients like spices, salt, and leavening are specified in teaspoons.

Used in: baking spices and leavening; liquid medicine dosing at home.

Imperial Gallon imp-gal also: imperial gallons, uk gallons

The imperial gallon is defined as exactly 4.54609 liters — about 20% larger than the US gallon. UK fuel economy figures (mpg) and older Commonwealth documents use it.

Used in: UK fuel economy figures; historical Commonwealth measurements.

Imperial Quart imp-qt also: imperial quarts, uk quarts

The imperial quart is a quarter of an imperial gallon, about 1.137 liters — larger than the US quart. It survives mainly in older UK recipes and trade documents.

Used in: older UK recipes; Commonwealth trade documents.

Imperial Pint imp-pt also: imperial pints, uk pints

The imperial pint is exactly 568.26125 milliliters — the legal measure for draft beer and cider in UK pubs, and about 20% larger than a US pint.

Used in: UK pub beer and cider servings; UK milk delivery.

Imperial Fluid Ounce imp-fl-oz also: imperial fluid ounces, uk fl oz

The imperial fluid ounce is about 28.413 milliliters, slightly smaller than the US fluid ounce, with 20 to the imperial pint rather than 16. Older UK packaging and recipes use it.

Used in: older UK packaging; traditional British recipes.

Cubic Foot ft3 also: cubic feet, ft³

The cubic foot is exactly 28.316846592 liters. US appliances (refrigerators, freezers), natural gas billing, and HVAC airflow (CFM) are specified in cubic feet.

Used in: US refrigerator and freezer capacity; natural gas billing; HVAC airflow ratings.

Cubic Inch in3 also: cubic inches, in³

The cubic inch is exactly 16.387064 milliliters. Classic American engine displacement and small US manufacturing volumes are quoted in cubic inches.

Used in: classic American engine displacement; US manufacturing part volumes.

Convert volume units →

Meters per Second mps also: m/s, meters/second

The meter per second is the SI derived unit of speed. Physics, wind reporting in many countries, and sprint analysis use it directly, and every other speed unit converts through it.

Used in: physics calculations; wind speed reporting in metric countries; sprint and athletics analysis.

Kilometers per Hour kph also: km/h, kmh, kilometers/hour

The kilometer per hour is the road speed unit of most of the world — exactly 1/3.6 of a meter per second. Speed limits, car speedometers, and rail and cycling speeds use it outside the US and UK.

Used in: road speed limits outside the US and UK; car and train speeds; cycling computers.

Miles per Hour mph also: mi/h, miles/hour

The mile per hour is exactly 1.609344 kilometers per hour, the road speed unit of the US and UK. Tennis serves, baseball pitches, and hurricane winds are also quoted in mph.

Used in: US and UK speed limits; ball sports speeds (pitches, serves); hurricane wind reports in the US.

Feet per Second fps also: ft/s, feet/second

The foot per second is exactly 0.3048 meters per second. US engineering uses it for projectile velocities, water flow, and conveyor speeds.

Used in: projectile and ballistics velocities; water flow in US civil engineering.

Knot knot also: knots, kn

The knot is one nautical mile per hour, exactly 1.852 km/h. Ships, aircraft, and weather charts use knots because the nautical mile maps onto latitude minutes.

Used in: ship and boat speeds; aircraft airspeed; marine weather forecasts.

Mach mach also: mach number

Mach number expresses speed as a multiple of the speed of sound — taken here as 343 meters per second, the value in dry air at 20 °C at sea level. Supersonic aircraft and missiles are rated in Mach.

Used in: supersonic aircraft speeds; aerospace engineering.

Speed of Light c also: light speed

The speed of light in a vacuum is exactly 299,792,458 meters per second — the universal speed limit, and the constant that defines the meter itself. Physics and astronomy express extreme speeds as fractions of c.

Used in: physics and relativity calculations; astronomy and spacecraft communication delays.

Convert speed units →

Byte B also: bytes

The byte is 8 bits, the basic addressable unit of computer storage. One byte holds a single ASCII character, and all file sizes build up from it.

Used in: file size fundamentals; network protocol fields; memory addressing.

Kilobyte KB also: kilobytes, kb

The kilobyte here is 1,024 bytes (the binary convention operating systems use, formally 'kibibyte'). Small documents, icons, and emails are kilobyte-scale.

Used in: text documents and emails; icons and small images.

Megabyte MB also: megabytes, mb

The megabyte here is 1,024 kilobytes, about a million bytes. Photos, songs, and app downloads are typically measured in megabytes.

Used in: photo and music file sizes; app download sizes; email attachment limits.

Gigabyte GB also: gigabytes, gb

The gigabyte here is 1,024 megabytes, about a billion bytes. RAM, phone storage, and mobile data plans are sold in gigabytes.

Used in: phone and laptop storage; RAM capacity; mobile data plans.

Terabyte TB also: terabytes, tb

The terabyte here is 1,024 gigabytes, about a trillion bytes. Hard drives, backup systems, and media libraries are terabyte-scale.

Used in: hard drive and SSD capacity; backup and archive storage.

Petabyte PB also: petabytes, pb

The petabyte here is 1,024 terabytes, about a quadrillion bytes. Data centers, scientific datasets, and large cloud platforms operate at petabyte scale.

Used in: data center capacity; scientific research datasets.

Bit bit also: bits

The bit is the smallest unit of digital information — a single 0 or 1. Network speeds are quoted in bits per second, which is why a '100 Mb' connection downloads at about 12.5 MB per second.

Used in: network bandwidth ratings; encryption key lengths.

Kilobit Kbit also: kilobits, kbit

The kilobit here is 1,024 bits, or 128 bytes. Audio bitrates and legacy modem speeds were quoted in kilobits per second.

Used in: audio streaming bitrates; legacy connection speeds.

Megabit Mbit also: megabits, mbit

The megabit here is 1,024 kilobits, or 128 kilobytes. Home internet speeds are advertised in megabits per second — divide by 8 for megabytes per second.

Used in: home internet speed plans; video streaming requirements.

Gigabit Gbit also: gigabits, gbit

The gigabit here is 1,024 megabits, or 128 megabytes. Fiber connections and modern LAN hardware ('gigabit ethernet') are rated in gigabits per second.

Used in: fiber internet plans; ethernet and LAN hardware speeds.

Terabit Tbit also: terabits, tbit

The terabit here is 1,024 gigabits, or 128 gigabytes. Internet backbone links and data center interconnects are measured in terabits per second.

Used in: internet backbone capacity; data center interconnects.

Convert data storage units →

Second s also: seconds, sec, secs

The second is the SI base unit of time, defined by 9,192,631,770 oscillations of the cesium-133 atom. Every other time unit is a multiple or fraction of it.

Used in: scientific measurement; sports timing; video and audio editing.

Millisecond ms also: milliseconds, msec

The millisecond is one thousandth of a second. Network latency, reaction times, and audio processing delays are quoted in milliseconds.

Used in: network ping and latency; human reaction times; audio latency.

Microsecond us also: microseconds, μs

The microsecond is one millionth of a second. High-frequency trading, GPS timing, and electronics signal measurement work at microsecond scale.

Used in: high-frequency trading latency; GPS and precision timing.

Nanosecond ns also: nanoseconds

The nanosecond is one billionth of a second — roughly the time light travels 30 cm. CPU clock cycles and memory access times are nanosecond-scale.

Used in: CPU and memory timings; physics experiments.

Minute min also: minutes, mins

The minute is 60 seconds. Cooking, meetings, exercise intervals, and per-minute billing all run on minutes.

Used in: cooking and recipes; meeting scheduling; exercise intervals.

Hour h also: hours, hr, hrs

The hour is 3,600 seconds (60 minutes). Work shifts, travel durations, and hourly wages are stated in hours.

Used in: work hours and wages; flight and travel durations; battery life ratings.

Day d also: days

The day is 86,400 seconds (24 hours). Deadlines, rental periods, and medication schedules count in days.

Used in: project deadlines; rental and subscription periods; medication schedules.

Week wk also: weeks, week

The week is 7 days, or 604,800 seconds. Payroll cycles, pregnancy tracking, and training plans are organized by weeks.

Used in: payroll and work schedules; pregnancy and medical tracking; training programs.

Month mo also: months, month

The month used here is one twelfth of a 365-day year — about 30.42 days or 2,628,000 seconds — since calendar months vary from 28 to 31 days. Billing cycles and age reporting use months.

Used in: subscription billing cycles; infant age tracking; loan terms.

Year yr also: years, year

The year used here is 365 days exactly (31,536,000 seconds), ignoring leap days. Ages, contracts, and interest rates are stated per year.

Used in: ages and anniversaries; contracts and interest rates; warranty periods.

Decade decade also: decades

The decade is 10 years — 3,650 days under this converter's 365-day year. Demographics, climate trends, and cultural eras are described in decades.

Used in: demographic and climate trends; career and life planning.

Century century also: centuries

The century is 100 years — 36,500 days under this converter's 365-day year. History, long-term climate records, and infrastructure lifespans span centuries.

Used in: historical periods; long-term climate records.

Convert time units →

Pascal Pa also: pascals, pa

The pascal is the SI derived unit of pressure — one newton per square meter. It is small for everyday pressures, so kilopascals and hectopascals appear more often in practice.

Used in: physics and engineering calculations; acoustics and sound pressure; material stress analysis.

Kilopascal kPa also: kilopascals, kpa

The kilopascal is 1,000 pascals. Tire pressures in metric countries, weather systems, and engineering specs commonly use kilopascals.

Used in: tire pressure in metric countries; HVAC and plumbing specifications; weather pressure changes.

Megapascal MPa also: megapascals, mpa

The megapascal is one million pascals, equal to one newton per square millimeter. Concrete strength, steel stress, and hydraulic systems are rated in megapascals.

Used in: concrete and steel strength ratings; hydraulic system pressures.

Bar bar also: bars

The bar is exactly 100,000 pascals, close to one atmosphere. European tire pressures, scuba tanks, and espresso machines are rated in bar.

Used in: European tire pressures; scuba diving tank pressure; espresso machine ratings.

Millibar mbar also: millibars, mb

The millibar is one thousandth of a bar, identical to the hectopascal. Meteorology has used millibars for surface pressure maps and storm intensity for a century.

Used in: weather maps and forecasts; hurricane intensity reporting; altimeter settings.

Atmosphere atm also: atmospheres, standard atmosphere

The standard atmosphere is defined as exactly 101,325 pascals — mean sea-level air pressure. Chemistry reference conditions and diving depth calculations use atmospheres.

Used in: chemistry reference conditions; diving depth pressure.

PSI psi also: pounds per square inch, lbf/in²

The pound per square inch is about 6,894.757 pascals. US tire pressures, water systems, and industrial equipment are rated in psi.

Used in: US tire pressure; US plumbing and well systems; industrial equipment ratings.

Torr torr also: torrs

The torr is exactly 1/760 of a standard atmosphere, about 133.32 pascals, named after Torricelli. Vacuum technology and laboratory work specify low pressures in torr.

Used in: vacuum systems and coating; laboratory low-pressure work.

mmHg mmHg also: millimeters of mercury, mm Hg

The millimeter of mercury is about 133.322 pascals — the height a pressure pushes a mercury column. Blood pressure worldwide is still reported in mmHg.

Used in: blood pressure readings; medical vacuum and ventilation.

inHg inHg also: inches of mercury, in Hg

The inch of mercury is about 3,386.39 pascals. US weather reports and aviation altimeter settings quote barometric pressure in inches of mercury.

Used in: US barometric weather reports; aviation altimeter settings.

Convert pressure units →

Joule J also: joule, joules

The joule is the SI derived unit of energy — the work done by a force of one newton over one meter. Physics, chemistry, and food labeling outside the US build on it.

Used in: physics and engineering calculations; food energy labeling outside the US.

Kilojoule kJ also: kilojoule, kilojoules

The kilojoule is 1,000 joules. Food energy in Australia, Europe, and most metric countries is labeled in kilojoules alongside or instead of calories.

Used in: food labels outside the US; exercise energy expenditure.

Megajoule MJ also: megajoule, megajoules

The megajoule is one million joules. Fuel energy density, gas billing in some countries, and crash test energies are quoted in megajoules.

Used in: fuel energy density figures; natural gas billing.

Gigajoule GJ also: gigajoule, gigajoules

The gigajoule is one billion joules, roughly the energy in 26 liters of gasoline. District heating and industrial energy contracts bill in gigajoules.

Used in: district heating bills; industrial energy contracts.

Calorie cal also: calorie, calories, small calorie

The calorie (small calorie) is exactly 4.184 joules — the thermochemical convention, originally the heat to warm one gram of water by 1 °C. Chemistry uses it; food 'Calories' are actually kilocalories.

Used in: chemistry heat calculations; scientific literature.

Kilocalorie kcal also: kilocalorie, kilocalories, food calorie

The kilocalorie is 4,184 joules — the food 'Calorie' (capital C) on US nutrition labels. Diet tracking and exercise burn estimates use kilocalories.

Used in: nutrition labels and diet tracking; exercise calorie burn.

Watt-hour Wh also: watt hour, watt-hour

The watt-hour is exactly 3,600 joules — one watt sustained for one hour. Battery capacities for phones, laptops, and e-bikes are rated in watt-hours.

Used in: battery capacity ratings; small device power consumption.

Kilowatt-hour kWh also: kilowatt hour, kilowatt-hour, kwh

The kilowatt-hour is exactly 3.6 megajoules — the unit on your electricity bill. Household consumption and electric vehicle battery sizes are stated in kilowatt-hours.

Used in: electricity billing; electric vehicle battery capacity; appliance energy ratings.

Megawatt-hour MWh also: megawatt hour, megawatt-hour

The megawatt-hour is 1,000 kilowatt-hours. Power plants, grid storage, and wholesale electricity markets trade in megawatt-hours.

Used in: wholesale electricity markets; grid-scale storage capacity.

British Thermal Unit BTU also: btu, british thermal unit

The British thermal unit is about 1,055.06 joules — the heat to raise one pound of water by 1 °F. US heating and cooling equipment is rated in BTU per hour.

Used in: air conditioner and furnace ratings in the US; US natural gas appliance specs.

Therm therm also: therms

The therm is 100,000 BTU, about 105.5 megajoules. US natural gas utilities bill household consumption in therms.

Used in: US natural gas billing; home heating cost estimates.

Foot-pound ft-lb also: foot-pound, foot pound, ft·lb

The foot-pound is about 1.3558 joules — the work of one pound-force through one foot. US mechanical engineering and firearm muzzle energy use foot-pounds.

Used in: US mechanical engineering; firearm muzzle energy.

Electronvolt eV also: electronvolt, electron volt

The electronvolt is exactly 1.602176634 × 10⁻¹⁹ joules — the energy an electron gains across one volt. Particle physics, semiconductors, and photon energies use electronvolts.

Used in: particle physics; semiconductor band gaps; photon energy calculations.

Erg erg also: erg, ergs

The erg is exactly 10⁻⁷ joules, the energy unit of the old CGS system. Astrophysics literature still quotes radiated energies in ergs.

Used in: astrophysics literature; historical scientific papers.

Convert energy units →

Degree deg also: degree, degrees, °

The degree is 1/360 of a full turn — a division inherited from Babylonian astronomy. Navigation, geometry, and everyday angle measurement default to degrees.

Used in: navigation headings; geometry and CAD drawings; camera field of view.

Radian rad also: radian, radians

The radian is the SI unit of angle: the angle whose arc length equals its radius, with 2π radians in a full turn. Calculus, physics, and programming math libraries work in radians.

Used in: physics and engineering formulas; programming math functions; rotational dynamics.

Milliradian mrad also: milliradian, milliradians

The milliradian is one thousandth of a radian, about 0.0573 degrees. Firearm scope adjustments and laser beam divergence are specified in milliradians.

Used in: rifle scope adjustments; laser beam specifications.

Gradian grad also: gradian, gradians, gon

The gradian (gon) is 1/400 of a full turn, making a right angle an even 100 gradians. European surveying and some calculators still support it.

Used in: European land surveying; calculator angle modes.

Turn turn also: turns, revolution, rev

The turn is one complete revolution — 360 degrees or 2π radians. Rotation counts, CSS animations, and mechanical engineering use full and fractional turns.

Used in: CSS and animation rotations; mechanical rotation counts.

Arcminute arcmin also: arcminute, arcminutes, arc minute

The arcminute is 1/60 of a degree. Astronomy quotes apparent sizes (the full Moon spans about 31 arcminutes) and optometry rates visual acuity in arcminutes.

Used in: astronomy apparent sizes; visual acuity measurement.

Arcsecond arcsec also: arcsecond, arcseconds, arc second

The arcsecond is 1/3600 of a degree, or 1/60 of an arcminute. Telescope resolution, star parallax (the basis of the parsec), and GPS precision use arcseconds.

Used in: telescope resolution; stellar parallax measurement.

Convert angle units →

Millihertz mHz also: millihertz

The millihertz is one thousandth of a hertz — one cycle every 1,000 seconds. Very slow oscillations like tides, building sway, and biological rhythms are measured in millihertz.

Used in: tidal and seismic oscillations; long-period structural monitoring.

Hertz Hz also: hertz

The hertz is the SI derived unit of frequency — one cycle per second, named after Heinrich Hertz. Sound pitch, mains electricity (50/60 Hz), and display refresh all measure in hertz.

Used in: audio pitch and tuning; mains power frequency; display refresh rates.

Kilohertz kHz also: kilohertz

The kilohertz is 1,000 hertz. AM radio frequencies, audio sample rates (44.1 kHz), and ultrasound run in the kilohertz range.

Used in: AM radio tuning; audio sample rates; ultrasonic devices.

Megahertz MHz also: megahertz

The megahertz is one million hertz. FM radio (87.5–108 MHz), older CPU clocks, and RAM speeds are quoted in megahertz.

Used in: FM radio frequencies; RAM and bus speeds.

Gigahertz GHz also: gigahertz

The gigahertz is one billion hertz. Modern CPU clock speeds, Wi-Fi bands (2.4/5/6 GHz), and mobile networks operate in gigahertz.

Used in: CPU clock speeds; Wi-Fi and mobile network bands.

Terahertz THz also: terahertz

The terahertz is one trillion hertz, between microwaves and infrared light. Security imaging, spectroscopy, and experimental wireless research work at terahertz frequencies.

Used in: spectroscopy research; security imaging technology.

Revolutions per Minute rpm also: revolutions per minute, rev/min

Revolutions per minute counts full rotations each minute — 1 rpm equals 1/60 Hz. Engine speeds, hard drives, and washing machine spin cycles are rated in rpm.

Used in: engine tachometer readings; appliance spin speeds; industrial motor ratings.

Revolutions per Second rps also: revolutions per second, rev/s

Revolutions per second counts full rotations each second — numerically equal to hertz for rotation. High-speed turbines and physics problems use rps where rpm numbers get unwieldy.

Used in: turbine and rotor engineering; physics rotation problems.

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Kilogram per Cubic Meter kg-m3 also: kg/m³, kg/m3

The kilogram per cubic meter is the SI derived unit of density. Air is about 1.2 kg/m³ and water about 1,000 kg/m³; engineering tables list materials in this unit.

Used in: engineering material tables; air density in aerodynamics; building material specs.

Gram per Cubic Centimeter g-cm3 also: g/cm³, g/cm3, g/cc

The gram per cubic centimeter equals exactly 1,000 kg/m³, with water at about 1 g/cm³. Chemistry, mineralogy, and metallurgy quote densities in g/cm³ because values land in a convenient 0–20 range.

Used in: chemistry lab work; mineral and metal identification.

Gram per Milliliter g-ml also: g/mL, g/ml

The gram per milliliter is identical to the gram per cubic centimeter, since 1 mL = 1 cm³. Liquid densities in cooking science, pharmacy, and lab protocols use g/mL.

Used in: pharmacy liquid formulations; laboratory solution preparation.

Gram per Liter g-l also: g/L, g/l

The gram per liter is one thousandth of a gram per milliliter, equal to 1 kg/m³. Solution concentrations, brewing sugar content, and gas densities are stated in g/L.

Used in: solution concentrations; brewing and winemaking measurements.

Kilogram per Liter kg-l also: kg/L, kg/l

The kilogram per liter equals exactly 1,000 kg/m³ — the same as g/cm³ and g/mL. Fuel and industrial liquid densities are often quoted in kg/L on safety data sheets.

Used in: fuel density specifications; industrial safety data sheets.

Milligram per Liter mg-l also: mg/L, mg/l

The milligram per liter equals one gram per cubic meter and, for dilute water solutions, approximates parts per million (ppm). Water quality limits and medical lab values use mg/L.

Used in: drinking water quality limits; medical blood test values.

Milligram per Cubic Meter mg-m3 also: mg/m³, mg/m3

The milligram per cubic meter is one millionth of a gram per liter. Air quality standards and workplace exposure limits for dust and pollutants are set in mg/m³.

Used in: air pollution standards; workplace exposure limits.

Pound per Cubic Foot lb-ft3 also: lb/ft³, lb/ft3

The pound per cubic foot is about 16.0185 kg/m³; water is roughly 62.4 lb/ft³. US construction and HVAC tables list material densities in lb/ft³.

Used in: US construction material tables; HVAC duct and insulation specs.

Pound per Cubic Inch lb-in3 also: lb/in³, lb/in3

The pound per cubic inch is 1,728 times denser than lb/ft³, about 27,680 kg/m³ — steel is roughly 0.28 lb/in³. US machining and aerospace use it for metal parts.

Used in: US machining stock weight; aerospace component design.

Ounce per Cubic Inch oz-in3 also: oz/in³, oz/in3

The ounce per cubic inch is one sixteenth of a pound per cubic inch, about 1,730 kg/m³. US casting, jewelry, and small-part work use it for compact material weights.

Used in: casting and mold calculations; jewelry making in the US.

Ounce per Gallon (US) oz-gal also: oz/gal

The ounce per US gallon is about 7.489 kg/m³. US recipe scaling, brewing additions, and chemical dosing in gallon-based systems use oz/gal.

Used in: brewing ingredient additions; US chemical dosing rates.

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Liters per 100 km L100km also: L/100km, l/100km, liters per 100km

Liters per 100 kilometers measures fuel consumption — lower is better. It is the official fuel economy figure in Europe, Australia, and most metric countries, and inverts the efficiency units used elsewhere.

Used in: European and Australian car specifications; fleet fuel budgeting.

Miles per Gallon (US) mpg-us also: mpg, mpg US, miles per gallon

Miles per US gallon measures distance per fuel — higher is better. It is the EPA window-sticker figure on every new car sold in the United States.

Used in: US car shopping and EPA ratings; US road trip fuel planning.

Miles per Gallon (Imperial) mpg-imp also: mpg imp, imperial mpg, UK mpg

Miles per imperial gallon uses the larger UK gallon (4.54609 L), so the same car scores about 20% higher than in US mpg. UK car reviews and older Commonwealth figures use it.

Used in: UK car reviews and adverts; comparing UK and US economy figures.

Kilometers per Liter km-l also: km/L, km/l, kilometres per litre

Kilometers per liter measures distance per unit fuel in metric terms — higher is better. Japan, India, and much of Asia and Latin America quote car economy in km/L.

Used in: car economy in Japan, India, and Asia; motorcycle fuel efficiency.

Liters per 100 miles l-100mi also: L/100mi, liters per 100 miles

Liters per 100 miles mixes metric fuel volume with mile distances — a hybrid unit appearing in some North American EV and plug-in hybrid comparisons alongside gallons-per-100-miles figures.

Used in: EV and hybrid consumption comparisons; mixed-unit fleet reporting.

Miles per Liter mi-l also: mi/L, miles per liter

Miles per liter measures mile distance per liter of fuel — useful where fuel is bought in liters but distances are driven in miles, as in the UK after metric fuel sales began.

Used in: UK fuel cost calculations; cross-border trip planning.

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Bit per Second bps also: bit/s, bits per second, b/s

The bit per second (bps) is the SI base unit of data transfer rate — the number of binary digits transmitted or processed per second. It is the reference from which all other data-rate units are derived.

Used in: serial port and modem specifications; low-bandwidth IoT sensor links; audio encoding bitrates below 64 kbps.

Kilobit per Second Kbps also: kbps, kbit/s, kilobits per second

The kilobit per second (Kbps) equals 1,000 bits per second (SI decimal prefix). It is the standard unit for slow internet connections, audio streaming, and legacy modem speeds.

Used in: dial-up and early DSL connections (56 Kbps – 1 Mbps); audio streaming (64–320 Kbps); SMS and low-data IoT networks.

Megabit per Second Mbps also: mbps, mbit/s, megabits per second

The megabit per second (Mbps) equals 1,000,000 bits per second (10⁶ bps). It is the dominant unit for consumer internet speed plans, Wi-Fi ratings, and video streaming requirements.

Used in: home broadband and cable internet (25–1,000 Mbps); Wi-Fi 5 and Wi-Fi 6 link rates; HD and 4K video streaming (5–25 Mbps); Ethernet LAN (100 Mbps Fast Ethernet, 1,000 Mbps Gigabit).

Gigabit per Second Gbps also: gbps, gbit/s, gigabits per second

The gigabit per second (Gbps) equals 1,000,000,000 bits per second (10⁹ bps). It is the standard for fibre-optic internet, data-centre interconnects, and NVMe storage throughput.

Used in: Gigabit and multi-gigabit fibre broadband (1–10 Gbps); data-centre server NICs and switches; NVMe SSD sequential read/write speeds (~5–14 Gbps); USB 3.2 Gen 2 (10 Gbps) and Thunderbolt 4 (40 Gbps).

Terabit per Second Tbps also: tbps, tbit/s, terabits per second

The terabit per second (Tbps) equals 10¹² bits per second. It is used for backbone fibre-optic cable capacity and inter-data-centre links. Single optical fibres can now carry over 10 Tbps using wavelength-division multiplexing.

Used in: submarine and intercontinental fibre-optic cables; hyperscale data-centre backbone links; CDN aggregate capacity reporting.

Byte per Second B-s also: B/s, bytes per second, byte/s

The byte per second (B/s) equals 8 bits per second. It is commonly used in file transfer progress indicators and storage benchmarks where download or copy speed is expressed in bytes rather than bits.

Used in: file download progress (browsers, torrent clients); storage copy speed in operating systems; API rate limits expressed in bytes/s.

Kilobyte per Second KB-s also: KB/s, kilobytes per second, kB/s

The kilobyte per second (KB/s) equals 8,000 bits per second (8 Kbps). It appears in file manager copy speed readouts and FTP transfer statistics.

Used in: file manager copy and move operations; FTP and SFTP transfer speed readouts; legacy modem file transfers.

Megabyte per Second MB-s also: MB/s, megabytes per second, mB/s

The megabyte per second (MB/s) equals 8,000,000 bits per second (8 Mbps). It is the standard unit for SSD and HDD benchmark results, USB transfer speeds, and file-copy throughput displays.

Used in: SSD sequential read/write benchmarks (500–7,000 MB/s); USB 3.0 (up to ~625 MB/s) and USB 3.2 transfers; file copy speed in Windows Explorer and macOS Finder; SATA SSD throughput (up to ~600 MB/s).

Gigabyte per Second GB-s also: GB/s, gigabytes per second

The gigabyte per second (GB/s) equals 8,000,000,000 bits per second (8 Gbps). It is used for high-end NVMe storage benchmarks, PCIe bandwidth, and GPU memory bandwidth specifications.

Used in: NVMe Gen 4/5 SSD throughput (5–14 GB/s); PCIe 4.0 × 16 bandwidth (~32 GB/s); GPU and CPU memory bandwidth (100–1,000 GB/s); DRAM bandwidth in servers.

Terabyte per Second TB-s also: TB/s, terabytes per second

The terabyte per second (TB/s) equals 8 × 10¹² bits per second (8 Tbps). It appears in GPU memory bandwidth comparisons (GDDR7, HBM3) and future storage architecture projections.

Used in: high-bandwidth memory (HBM) GPU bandwidth; future NVMe and CXL storage projections; aggregate NVMe RAID array throughput.

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