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Fuel Economy Converter
Convert fuel economy between US MPG, UK MPG, liters per 100 km, kilometers per liter and miles per liter. Turn on the comparison to see how much fuel and money two vehicles use per year.
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Optional. Enter today's local price.
Enter your values to see the result.
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How to use the Fuel Economy Converter
- Enter vehicle A's fuel economy and its unit, for example 30 US MPG.
- Choose the unit to convert to; all other units show in the results.
- Tick Compare and enter vehicle B's figure in any unit.
- Add your yearly distance and fuel price to see the fuel and cost difference.
- Copy the results or download the comparison table.
Fuel economy formulas
Two families of units exist. Distance per fuel (MPG, km/L, mi/L): higher is better. Fuel per distance (L/100 km): lower is better. The converter goes through km per liter, using 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L and 1 UK gallon = 4.54609 L.
L/100 km = 235.215 ÷ US MPGandUS MPG = 235.215 ÷ L/100 kmL/100 km = 282.481 ÷ UK MPGUS MPG = km/L × 2.352146andUK MPG = km/L × 2.824809UK MPG = US MPG × 1.200950mi/L = km/L ÷ 1.609344andL/100 km = 100 ÷ km/L
Example: 7.84 L/100 km → 100 ÷ 7.84 = 12.76 km/L → 12.76 × 2.352 = 30.0 US MPG → 30.0 × 1.201 = 36.0 UK MPG.
Fuel economy equivalents
| L/100 km | US MPG | UK MPG | km/L |
|---|---|---|---|
| 4 | 58.8 | 70.6 | 25.0 |
| 5 | 47.0 | 56.5 | 20.0 |
| 6 | 39.2 | 47.1 | 16.7 |
| 7 | 33.6 | 40.4 | 14.3 |
| 8 | 29.4 | 35.3 | 12.5 |
| 10 | 23.5 | 28.2 | 10.0 |
| 12 | 19.6 | 23.5 | 8.3 |
| 15 | 15.7 | 18.8 | 6.7 |
Comparing vehicles fairly
- Compare fuel used over your real yearly distance, not the MPG gap: the same MPG improvement saves far more fuel on a thirsty vehicle.
- Use the same test basis for both vehicles (for example US EPA combined vs WLTP), because different test cycles give different numbers.
- Real-world economy depends on speed, climate, tire pressure, load and driving style; expect it to differ from official ratings.
- Fuel prices change often, so enter your current local price for the cost comparison.
Frequently asked questions
How do I convert MPG to L/100 km?
Divide 235.215 by the US MPG figure: 30 MPG = 235.215 ÷ 30 = 7.84 L/100 km. For UK MPG use 282.481 instead: 30 UK MPG = 9.42 L/100 km. The same formulas work in reverse.
Why are UK MPG figures higher than US MPG?
An imperial gallon is 4.546 liters, about 20% more than a US gallon of 3.785 liters, so a car goes further on one. 1 UK MPG = 0.8327 US MPG; a car rated 50 UK MPG is about 41.6 US MPG.
How do I convert km/L to MPG?
Multiply km/L by 2.352146 for US MPG (or by 2.824809 for UK MPG). 15 km/L is about 35.3 US MPG. To convert L/100 km to km/L, divide 100 by the L/100 km figure.
Why does a lower L/100 km mean better economy?
L/100 km measures fuel used per distance, so less is better. MPG and km/L measure distance per unit of fuel, so more is better. That is why converting between them needs a division, not a multiplication.
Is going from 20 to 25 MPG worth more than 40 to 50 MPG?
Yes, over the same distance. For 10,000 miles, 20 → 25 MPG saves 100 gallons (500 − 400), while 40 → 50 MPG saves only 50 gallons (250 − 200). Fuel use follows L/100 km or gallons per mile, not MPG.
What is a good fuel economy?
It depends on the vehicle type, but many new US gasoline cars are rated around 25-35 MPG combined (about 6.7-9.4 L/100 km), and many hybrids are 45-55 MPG (about 4.3-5.2 L/100 km).
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
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