Fuel Economy Converter: mpg (US, UK), km/L, L/100 km
Convert US mpg, UK mpg, km per litre and litres per 100 km, with the working shown.
Inputs
- Miles per gallon (US)
- 30.00
- Litres per 100 km
- 7.84
- Miles per gallon (UK)
- 36.03
- Working
- 30 mi ÷ 1 US gal = 30 × 1.609344 km ÷ 3.785411784 L = 12.754 km/L; L/100 km = 100 ÷ 12.754 = 7.84
- A UK gallon is 4.54609 L and a US gallon 3.785411784 L (NIST SP 811), so the same car shows a UK mpg about 20% higher than its US mpg.
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What each Fuel Economy input means
- Value
- The fuel economy figure you have: from a car's spec sheet, its trip computer or your own fill-ups.
- From
- km/L (used in India, Japan and Latin America), US mpg, UK mpg or L/100 km (Europe, Canada, Australia). The page shows all four at once.
Fuel Economy conversion formula
km/L = US mpg × 1.609344 ÷ 3.785412 · L/100 km = 100 ÷ km/L = 235.215 ÷ US mpg · UK mpg = US mpg × 1.20095
Two ways of measuring fuel economy run in opposite directions. Miles per gallon and kilometres per litre are distance per fuel — bigger is better. Litres per 100 km is fuel per distance — smaller is better — so it is the reciprocal, not a multiple: L/100 km = 100 ÷ (km/L). The gallon matters too: a UK (imperial) gallon is 4.546 L against the US gallon's 3.785, so the same car's UK mpg is about 20% higher than its US mpg. The page converts through km/L and shows all four.
Fuel Economy conversion worked example
30 US mpg × 1.609344 ÷ 3.785412 = 12.75 km/L, and 100 ÷ 12.75 = 7.84 L/100 km. In the UK the same car would be quoted at 36.03 mpg, because the British gallon is bigger.
More Fuel Economy examples
A European rating of 6.5 L/100 km: 100 ÷ 6.5 = 15.38 km/L, which is 36.19 US mpg and 43.46 UK mpg.
A UK figure of 45 mpg: 45 × 1.609344 ÷ 4.54609 = 15.93 km/L — 37.47 mpg in US gallons, 6.28 L/100 km.
A small car rated at 20 km/L stays 20.00 km/L in the headline and is 47.04 US mpg, 5 L/100 km.
Where the Fuel Economy converter can give the wrong answer
- Because L/100 km is a reciprocal, equal steps in mpg are not equal savings: going from 10 to 20 mpg saves far more fuel than going from 40 to 50.
- Official figures (EPA in the US, WLTP in Europe) use different test cycles; converting units does not make them comparable.
- Electric-vehicle efficiency (kWh per 100 miles, MPGe) is a different measure and is not converted here.
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Fuel Economy conversion reference table
| US mpg | L/100 km | km/L | UK mpg |
|---|---|---|---|
| 15 | 15.68 | 6.38 | 18 |
| 20 | 11.76 | 8.5 | 24 |
| 25 | 9.41 | 10.63 | 30 |
| 30 | 7.84 | 12.75 | 36 |
| 35 | 6.72 | 14.88 | 42 |
| 40 | 5.88 | 17.01 | 48 |
| 45 | 5.23 | 19.13 | 54 |
| 50 | 4.7 | 21.26 | 60 |
| 60 | 3.92 | 25.51 | 72.1 |
Fuel Economy conversion FAQ
- Divide 235.215 by US mpg: 30 mpg is 7.84 L/100 km. For UK mpg, divide 282.48 instead.
- The imperial gallon is 4.546 L and the US gallon 3.785 L, so a car goes about 20% further on a UK gallon. Multiply US mpg by 1.201 for UK mpg.
- Multiply by 2.352 for US mpg (or 2.825 for UK mpg). 15 km/L is 35.28 US mpg.
- Yes. It is litres burned per 100 km, so less is better — the opposite of mpg.
- 47.0 US mpg, or 56.5 UK mpg: 235.215 ÷ 5 and 282.481 ÷ 5.
- Divide 100 by it: 15 km/L is 6.67 L/100 km. The same division works in reverse.
- Divide the litres needed to refill the tank by the kilometres driven since the last fill, then multiply by 100: 42 L after 600 km is 7 L/100 km.
- 5.88 L/100 km in US gallons; 40 UK mpg is 7.06 L/100 km.
- Multiply US mpg by 0.425 (1.609344 ÷ 3.785412): 30 mpg is 12.75 km/L. For UK mpg, multiply by 0.354.
- In kWh per 100 km or miles per kWh — or, on US window stickers, in MPGe, where the EPA counts 33.7 kWh as one gallon of gasoline. Those are not convertible to L/100 km on this page.
- 23.5 US mpg, or 28.2 UK mpg.
- 29.4 US mpg, or 35.3 UK mpg: 235.215 ÷ 8 and 282.481 ÷ 8.
- 9.41 L/100 km for US gallons: 235.215 ÷ 25.
- 35 US mpg is 6.72 L/100 km, so the 35 mpg car uses slightly less fuel.
- 39.2 US mpg, or 47.1 UK mpg.