Fuel Economy Converter
Enter a fuel economy figure and see it in US mpg, UK mpg, litres per 100 km and kilometres per litre.
Remember that for L/100 km a smaller number is more economical, while for mpg and km/L a bigger number is.
What this tool does
Fuel economy is quoted in miles per gallon in the US and UK and litres per 100 km in most of the rest of the world. They are reciprocals: L/100 km = 235.215 ÷ US mpg, or 282.481 ÷ UK mpg. So 30 US mpg is 7.84 L/100 km. Enter any figure above to see all four units.
Converts any one fuel economy figure into US mpg, UK mpg, L/100 km and km/L at once.
Includes quick buttons for typical values and a reminder of which direction means "better".
How to use it
- Enter the value.
- Choose the unit it is in.
- Read the four results.
- Use the quick buttons to try typical values.
Why use this converter
Converts between US mpg, UK mpg, litres per 100 km and kilometres per litre in one step. A car advertised at 40 mpg in one market is 5.9 L/100 km in another, and the US and UK gallons differ by about 20%, so the same car has two different mpg numbers. Converting makes cars and fuel claims comparable.
Why we built it
We built the fuel economy converter to show US mpg, UK mpg, L/100 km and km/L at once, with a reminder that smaller L/100 km is better. Work out trip costs with the fuel cost calculator and convert fuel volumes with the litres to gallons converter.
For a neighbouring job there is also the HP to kW Converter.
Related tools worth a look: the MPG Calculator.
Who this tool is for
- Car buyers comparing models from different markets
- Drivers moving between countries
- Writers and reviewers
When to use it
- Comparing cars from different markets.
- Understanding a fuel economy label or review.
- Estimating running costs abroad.
- Converting trip computer figures.
How it works
Everything is converted through litres per 100 km. A US gallon is 3.785411784 litres and a UK gallon is 4.54609 litres, and a mile is 1.609344 km, so US mpg = 235.2145833 ÷ (L/100 km), UK mpg = 282.4809363 ÷ (L/100 km), and km/L = 100 ÷ (L/100 km).
| US mpg | UK mpg | L/100 km | km/L |
|---|---|---|---|
| 20 | 24.0 | 11.8 | 8.5 |
| 25 | 30.0 | 9.4 | 10.6 |
| 30 | 36.0 | 7.8 | 12.8 |
| 35 | 42.0 | 6.7 | 14.9 |
| 40 | 48.0 | 5.9 | 17.0 |
| 50 | 60.0 | 4.7 | 21.3 |
For mpg and km/L a higher number is more economical. For L/100 km a lower number is more economical.
What you give it, and what you get back
| Item | Details |
|---|---|
| Value | A fuel economy figure greater than zero. |
| Unit | US mpg, UK mpg, L/100 km or km/L. |
| Output | All four units, ready to copy. |
Issues you may run into
| What you see | Why it happens | What to do |
|---|---|---|
| Result is 20% off a published figure | US and UK mpg were confused. | Choose the unit your source uses. |
| Better and worse feel reversed | L/100 km is lower for better economy. | Compare numbers in the same unit. |
| Zero or negative is refused | Fuel economy must be positive. | Enter a positive number. |
Assumptions and limitations
- Converts a single figure; real-world economy varies with driving, load and weather.
- Uses US and UK gallon definitions explicitly.
- It does not estimate fuel cost - use the fuel cost calculator.
Frequently asked questions
How do I convert mpg to L/100 km?
Divide 235.215 by the mpg (US) or 282.481 by the mpg (UK).
What is 30 mpg in L/100 km?
30 US mpg is 7.84 L/100 km; 30 UK mpg is 9.42 L/100 km.
Why do US and UK mpg differ?
A UK gallon is about 20% larger than a US gallon, so the same car has a higher UK mpg figure.
Is a higher or lower L/100 km better?
Lower. It is fuel used per distance, so smaller means more economical.
How do I convert km/L to mpg?
Convert to L/100 km (100 ÷ km/L) then divide 235.215 by it for US mpg.
Is it free and private?
Yes. It runs in your browser.