mpg · L/100 km · km/L
Fuel economy converter
30 miles per US gallon is 7.84 litres per 100 km, or 9.42 L/100 km if the gallon is imperial. Enter a fuel economy, pick a unit and read it in all five units at once.
- 30 mpg (US) = 7.840486 L/100 km
- 30 L/100 km = 7.840486 mpg (US)
The result and the table below it update as you type. Zero has no equivalent in another unit, so it shows an error. Only the printed figure is rounded, to six significant digits.
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At a glance
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- Not applicable — you type a value, nothing is sent anywhere
- Units
- Mile per US gallon, mile per imperial gallon, kilometre per litre, mile per litre and litre per 100 km
- Definitions
- Mile 1.609344 km, US gallon 3.785411784 L, imperial gallon 4.54609 L
- Works on
- Any modern browser
Common fuel economy conversions
These tables are computed from the same definitions as the converter. Read each one left to right: the first column is the value you start with and the second is its equivalent.
| mpg (US) | L/100 km |
|---|---|
| 20 | 11.7607 |
| 30 | 7.84049 |
| 40 | 5.88036 |
| 50 | 4.70429 |
| L/100 km | mpg (US) |
|---|---|
| 20 | 11.7607 |
| 30 | 7.84049 |
| 40 | 5.88036 |
| 50 | 4.70429 |
| mpg (UK) | L/100 km |
|---|---|
| 20 | 14.124 |
| 30 | 9.41603 |
| 40 | 7.06202 |
| 50 | 5.64962 |
| mpg (US) | mpg (UK) |
|---|---|
| 20 | 24.019 |
| 30 | 36.0285 |
| 40 | 48.038 |
| 50 | 60.0475 |
| mpg (US) | km/L |
|---|---|
| 20 | 8.50287 |
| 30 | 12.7543 |
| 40 | 17.0057 |
| 50 | 21.2572 |
| km/L | L/100 km |
|---|---|
| 20 | 5 |
| 30 | 3.33333 |
| 40 | 2.5 |
| 50 | 2 |
How to convert a fuel economy
Enter the figure
Type the number from the car's data sheet or trip computer in the first field, such as 30 for 30 mpg or 7.5 for 7.5 L/100 km.
Pick the two units
Choose the unit you have in the first menu and the unit you want in the second. Check whether your mpg figure is US or imperial, because the two differ by about 20 percent.
Read the table
The large figure is your answer. The table lists the same fuel economy in all five units, so you can copy the one you need without converting again.
How fuel economy conversion works
Fuel economy is quoted in two opposite ways. Miles per gallon and kilometres per litre count distance per volume of fuel, so a higher figure means a more efficient car. Litres per 100 km counts volume per distance, so a lower figure is better. This page converts everything through kilometres per litre: one mile is exactly 1.609344 km, one US gallon is exactly 3.785411784 litres, and one imperial gallon is exactly 4.54609 litres.
Between mpg and L/100 km the conversion is a reciprocal, not a multiplication: L/100 km equals 235.2146 divided by mpg (US), or 282.4809 divided by mpg (imperial). That is why doubling the mpg halves the L/100 km: 20 mpg is 11.7607 L/100 km and 40 mpg is 5.88036. A figure of zero cannot be converted between a distance-per-volume unit and L/100 km, because it would need a division by zero, so the page shows an error instead. Real consumption also depends on speed, load and test cycle, and this tool converts the unit only.
Fuel economy conversion questions
How do I convert mpg to L/100 km?
Divide 235.2146 by the mpg figure for US gallons. 30 mpg (US) is 235.2146 ÷ 30 = 7.84049 L/100 km, and 20 mpg is 11.7607 L/100 km. For imperial gallons divide 282.4809 by the figure: 30 mpg (UK) is 9.41603 L/100 km.
Why is a lower L/100 km number better but a higher mpg number better?
They measure opposite things. Miles per gallon is distance travelled on a fixed amount of fuel, so more is better. Litres per 100 km is fuel burned over a fixed distance, so less is better. Each is the reciprocal of the other, so 50 mpg (US) is 4.70429 L/100 km while 25 mpg is 9.40858.
Why do US mpg and imperial mpg differ?
The gallons are different sizes. A US gallon is 3.785411784 litres and an imperial gallon is 4.54609 litres, a ratio of 4.54609 ÷ 3.785411784 = 1.2009. The same car therefore shows a figure about 20 percent higher in imperial mpg: 30 mpg (US) is 36.0285 mpg (UK), and 30 mpg (UK) is 24.9802 mpg (US).
What is 8 L/100 km in mpg?
8 L/100 km is 29.4018 mpg in US gallons and 35.3101 mpg in imperial gallons, which is also 12.5 km/L. Divide 235.2146 by 8 for the US figure.
Do my numbers leave my device?
No. The arithmetic runs in your browser, so nothing you type is sent anywhere. With the page already loaded, the converter also works offline.