Fuel Consumption Converter
With figure you have 32, fuel price 3.4 usd, distance driven a year 12000 miles, fuel consumption converter comes to 7.35 L/100km — liters per 100 km. It is reached in 6 steps, the last of which is 235.21458 / 32, and each one is printed on the page with its numbers filled in. The formula is the one published by NIST Handbook 44, Appendix C, not an approximation fitted to it.
Miles per gallon, liters per 100 km and kilometers per liter from any one of them, with the US and imperial gallons kept apart.
Formula and sources checked · How we check
Figure you have 32, In these units Miles per US gallon, Fuel price 3.4, Distance driven a year 12000 miles
7.35 L/100km
Liters per 100 km for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Miles per US gallon
32 mpg- Miles per imperial gallon
32 * 1.2009538.43 mpg- Liters per 100 km
235.21458 / 327.35 L/100km- Kilometers per liter
32 / 2.352145813.605 km/L- Gallons a year
12000 / 32375 gal- Fuel cost a year
375 * 3.4$1,275
Worked example
32 US mpg is 7.35 liters per 100 km — and 38.4 miles per imperial gallon, which is the same car quoted in British units. The 20% between the two gallons is why a UK review of an American car always reads better than the American one.
How to work it out yourself
- 1.Pick the units your figure is actually in. A British brochure quotes imperial gallons and a US window sticker quotes US gallons, and they differ by twenty per cent.
- 2.Note that liters per 100 km runs the other way: a lower number is better, and the relationship to mpg is a reciprocal rather than a scale.
- 3.Add the fuel price and your annual mileage if you want the yearly cost — that is the figure a fuel-economy difference actually means.
Miles per gallon in metric units
| Figure you have | Liters per 100 km | Liters per 100 km | Miles per imperial gallon |
|---|---|---|---|
| 15 | 15.68 L/100km | 15.68 L/100km | 18.01 mpg |
| 20 | 11.76 L/100km | 11.76 L/100km | 24.02 mpg |
| 25 | 9.41 L/100km | 9.41 L/100km | 30.02 mpg |
| 30 | 7.84 L/100km | 7.84 L/100km | 36.03 mpg |
| 35 | 6.72 L/100km | 6.72 L/100km | 42.03 mpg |
| 40 | 5.88 L/100km | 5.88 L/100km | 48.04 mpg |
| 45 | 5.23 L/100km | 5.23 L/100km | 54.04 mpg |
| 50 | 4.70 L/100km | 4.7 L/100km | 60.05 mpg |
| 60 | 3.92 L/100km | 3.92 L/100km | 72.06 mpg |
| 70 | 3.36 L/100km | 3.36 L/100km | 84.07 mpg |
Entered as miles per US gallon.
The formula
- Miles per US gallon
- Miles per imperial gallon
32 * 1.20095 - Liters per 100 km
235.21458 / 32 - Kilometers per liter
32 / 2.3521458 - Gallons a year
12000 / 32 - Fuel cost a year
375 * 3.4
Source: NIST Handbook 44, Appendix C — general tables of units of measurement
Questions people actually ask
- Why is a British mpg figure always higher?
- Because the imperial gallon is 4.546 liters against the US gallon’s 3.785 — twenty per cent more fuel per gallon, and therefore twenty per cent more miles from one. A car doing 32 mpg in the US does 38.4 mpg in the UK without anything about the car changing.
- Why does the rest of the world measure liters per 100 km?
- Because it scales the way costs do. Fuel used per distance is what you pay for, and it adds up linearly: two journeys at 8 L/100 km average 8. Miles per gallon is a reciprocal, so averaging two mpg figures is simply wrong — a car doing 10 mpg and one doing 50 mpg average 16.7 mpg over the same distance, not 30.
- What is the conversion factor?
- 235.214583 divided by the figure, in either direction. It is 100 kilometers expressed in miles multiplied by the liters in a US gallon, so it is exact rather than measured. For imperial gallons the constant is 282.481.
- Is a 5 mpg improvement worth the same at every level?
- No, and this is where mpg misleads badly. Going from 15 to 20 mpg saves 167 gallons over 10,000 miles; going from 40 to 45 saves 28. The same five-mpg step is worth six times more at the bottom of the range, which is why replacing the thirstiest vehicle in a fleet matters more than improving the most efficient one.
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