Fuel Economy Converter

Fuel economy quantifies how efficiently a vehicle uses fuel over distance. The metric system expresses it as volume consumed per distance (L/100 km) — a direct measure of fuel consumption. The US and UK use the inverse form: distance per volume (miles per gallon, mpg). Because the US and imperial gallon differ by 20% (3.785 L vs 4.546 L), US mpg and imperial mpg ratings are not interchangeable for the same vehicle. The kilometre per litre (km/L) used in Japan is the mathematical reciprocal of L/100 km, scaled by 100.

All conversions in this category are computed relative to a single base unit — Liters per 100 km — using factors sourced from NIST Special Publication 811 and the BIPM SI Brochure. Anchoring every conversion to one reference unit guarantees mathematical consistency: converting from A → B → C always yields the same result as converting directly from A → C.

Among the 6 supported units, the most frequently used include Liters per 100 km, Miles per Gallon (US), Miles per Gallon (Imperial), Kilometers per Liter, Liters per 100 miles. These appear across household tasks, professional environments, and academic study.

Many units carry aliases and regional abbreviations that appear in product specs, recipes, and technical documents. We index common synonyms so searches for alternate spellings still reach the right converter — for example, Liters per 100 km (L100km, also written as L/100km or l/100km), or Miles per Gallon (US) (mpg-us, also written as mpg or mpg US), or Miles per Gallon (Imperial) (mpg-imp, also written as mpg imp or imperial mpg).

Because fuel economy scales have different zero points or non-linear relationships, conversions require specific formulas rather than simple multiplication. Each converter page shows the exact formula for that pair, along with a worked example and a reference table.

For calculations requiring extended precision — chemistry, engineering tolerances, financial modelling — the converter outputs unrounded values so you can apply your own rounding policy. The formula and factor displayed on each page are the same values used internally, so you can reproduce any result by hand.

In daily practice, choosing the right fuel economy unit saves time and prevents costly errors. Commercial shipping, construction, and scientific research all depend on correct unit handling to maintain safety, compliance, and reproducibility across borders and disciplines.

Consumer products, regulations, and international standards often specify values in different unit systems — a drug dosage in micrograms, a fuel efficiency in L/100 km, a tyre pressure in PSI. Each domain has a dominant unit, and cross-domain work requires reliable conversion. This converter is built for exactly those situations: results traceable to internationally defined constants, displayed with full precision.