Fuel Economy Converter: L/100 km, km/L, US MPG and UK MPG

Two different ways to measure fuel economy

Most of Europe, Australia, Canada and many other countries give fuel consumption: liters used per 100 km. Lower is better. The United States and the United Kingdom give fuel economy: miles traveled per gallon. Higher is better. Parts of Asia and Latin America use kilometers per liter, also higher-is-better.

Because one measure is the reciprocal of the other, the conversion divides rather than multiplies:

mpg (US) = 235.215 ÷ L/100 km mpg (UK) = 282.481 ÷ L/100 km km/L = 100 ÷ L/100 km

The constants come from the exact unit definitions: 100 × 3.785411784 L ÷ 1.609344 km ≈ 235.215 for US gallons, and 100 × 4.54609 L ÷ 1.609344 km ≈ 282.481 for imperial gallons. The calculator uses the exact values, not the rounded constants.

Example: a car rated at 6.5 L/100 km does 235.2146 ÷ 6.5 = 36.2 miles per US gallon, or 43.5 miles per imperial gallon.

Why UK mpg is higher than US mpg for the same car

An imperial gallon (4.55 L) is about 20% larger than a US gallon (3.79 L), so a car goes further on one. The same car shows a higher mpg figure in the UK than in the US: multiply US mpg by about 1.201 to get UK mpg.

Fuel consumption conversion table (rounded to 0.1)
L/100 km	km/L	mpg (US)	mpg (UK)
4 L/100 km	25.0	58.8	70.6
5 L/100 km	20.0	47.0	56.5
6 L/100 km	16.7	39.2	47.1
7 L/100 km	14.3	33.6	40.4
8 L/100 km	12.5	29.4	35.3
10 L/100 km	10.0	23.5	28.2
12 L/100 km	8.3	19.6	23.5
15 L/100 km	6.7	15.7	18.8

Official ratings are not directly comparable

Even after converting units, official figures from different countries are measured on different test cycles (for example the WLTP procedure in the EU and UK and the EPA procedures in the US) and are not directly comparable. Real-world consumption also depends on speed, load, weather and driving style.

Common questions

Why does saving fuel look different in mpg and L/100 km?

Going from 10 to 20 mpg saves far more fuel than going from 40 to 50 mpg, even though both are “+10 mpg”. L/100 km is proportional to fuel used, so equal changes mean equal savings. For comparing running costs, L/100 km (or its equivalent gallons per 100 miles) is easier to reason about.

Can I enter zero?

No. Zero liters per 100 km or zero miles per gallon has no meaningful equivalent in the other units (it would be infinite), so the converter asks for a value greater than zero.