Enter the fuel economy and choose from US miles per gallon, imperial miles per gallon, liters per 100 kilometers and kilometers per liter. A higher mpg or km/L number means better efficiency, while a higher L/100 km number means worse efficiency, since it measures fuel used per distance. Take the value from a vehicle label or your own tank-to-tank calculation.
Imperial gallons are about 20% larger than US gallons, so imperial mpg figures are higher.
Fuel Economy Converter: worked example
| Fuel Economy to convert | 30 |
|---|---|
| Starting unit | Miles per gallon (US) |
| Requested unit | Liters per 100 km |
| Converted value | 7.84 |
| Same economy in L/100 km | 7.84 |
Fuel Economy Converter: formula
Common error: Averaging the ratings of two cars in miles per gallon to guess a combined figure. The fuel used adds up in liters per distance, so the arithmetic average is wrong.
US and imperial gallons differ, so 30 US mpg is about 36 imperial mpg. Real-world economy varies with speed, load, traffic and temperature, and label ratings are test-cycle figures. The metric figures use kilometers, and the tool does not handle electric vehicle efficiency measured in kilowatt-hours per 100 miles.
Fuel Economy Converter: changing Fuel Economy to convert
| Fuel Economy to convert | Converted value | Same economy in L/100 km |
|---|---|---|
| 24 | 9.80 | 9.80 |
| 27 | 8.71 | 8.71 |
| 30 (example) | 7.84 | 7.84 |
| 33 | 7.13 | 7.13 |
| 36 | 6.53 | 6.53 |
Fuel Economy Converter: compare input ranges
| Input | Tested from | To | Converted value: low input | Converted value: high input | Swing |
|---|---|---|---|---|---|
| Starting unit | Miles per gallon (US) | Kilometers per liter | 7.84 | 3.33 | 4.51 (340%) |
| Requested unit | Miles per gallon (US) | Kilometers per liter | 30.00 | 12.75 | 17.25 (360%) |
| Fuel Economy to convert | 27 | 33 | 8.71 | 7.13 | 1.58 (20%) |
Fuel Economy Converter: individual input comparisons
| Input | Value | Converted value | Same economy in L/100 km |
|---|---|---|---|
| Fuel Economy to convert | 24 | 9.80 | 9.80 |
| 27 | 8.71 | 8.71 | |
| 30 | 7.84 | 7.84 | |
| 33 | 7.13 | 7.13 | |
| 36 | 6.53 | 6.53 | |
| Starting unit | Miles per gallon (US) | 7.84 | 7.84 |
| Miles per gallon (imperial) | 9.42 | 9.42 | |
| Liters per 100 km | 30.00 | 30.00 | |
| Kilometers per liter | 3.33 | 3.33 | |
| Requested unit | Miles per gallon (US) | 30.00 | 7.84 |
| Miles per gallon (imperial) | 36.03 | 7.84 | |
| Liters per 100 km | 7.84 | 7.84 | |
| Kilometers per liter | 12.75 | 7.84 |
Fuel Economy Converter: which assumptions move the result?
Fuel Economy Converter: values and definitions
| Quantity and definition | Value used |
|---|---|
| Fuel Economy to convert | 30 |
| Starting unit — Unit to convert from. | Miles per gallon (US) |
| Requested unit — Unit to convert to. | Liters per 100 km |
| Converted value | 7.84 |
| Same economy in L/100 km | 7.84 |
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Fuel economy is quoted in opposite directions: miles per gallon says how far one gallon goes, and liters per 100 kilometers says how much fuel a distance takes. That inversion makes the conversion nonlinear. Thirty US miles per gallon is about 7.84 liters per 100 kilometers, and thirty imperial miles per gallon is about 9.42, because the imperial gallon is larger.
The unit of the gallon decides the answer. Reference values: 25 US mpg is about 9.4 liters per 100 kilometers, 40 US mpg is about 5.9 and 50 US mpg is about 4.7. One US mpg is about 0.425 kilometers per liter.
Check which gallon a rating uses. A UK figure in miles per gallon is imperial, and the same number in the US means a smaller gallon and less distance.
Estimate annual fuel cost on the fuel cost calculator, compare with electric options on the EV vs gas calculator, and plan a trip on the trip cost page. The volume converter changes gallons and liters, and the length converter changes miles and kilometers. The vehicle total cost of ownership page adds the rest.
How do I convert mpg to liters per 100 km?
Divide 235.2 by the US mpg figure. So 30 mpg is about 7.84 liters per 100 kilometers.
Why do imperial mpg numbers look higher?
Because an imperial gallon is about 20% larger than a US gallon, so a car goes further on one imperial gallon.
Which is better, higher mpg or lower L/100 km?
Both mean better efficiency. Higher mpg and lower liters per 100 kilometers mean less fuel used for the same distance.