Gas Mileage Calculator
Choose the units you measured in, then enter the distance you drove and the fuel you used. The calculator gives your fuel economy in miles per US gallon, miles per UK gallon, liters per 100 km and kilometers per liter.
Your numbers
How we calculate it
Everything is turned into kilometers and liters with exact constants: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 liters and 1 UK (imperial) gallon = 4.54609 liters. Kilometers per liter is km ÷ liters, and liters per 100 km is 100 ÷ that.
Miles per gallon is miles ÷ gallons in the unit you pick. 300 miles on 10 US gallons is 30 miles per US gallon, which is 36.03 miles per UK gallon, 7.84 liters per 100 km and 12.75 km per liter.
Assumptions and limits
- A US gallon and a UK gallon are different sizes, so the same car has a higher figure in miles per UK gallon.
- For the most accurate figure, fill the tank, drive, and fill it again, then use the fuel you added.
- Lower liters per 100 km is better, while higher miles per gallon and kilometers per liter are better.
Frequently asked questions
How do I calculate miles per gallon?
Divide the miles you drove by the gallons of fuel you used. 300 miles on 10 gallons is 30 miles per gallon.
Why are US and UK miles per gallon different?
The gallons are different sizes. A UK gallon is about 20% larger than a US gallon, so the same trip gives a bigger number in UK miles per gallon.
How do I convert MPG to liters per 100 km?
Divide 235.215 by the miles per US gallon. For UK miles per gallon, divide 282.481 by the figure. The calculator does it for you.
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Worked example (a fixed example using the starting numbers, it does not change as you type)
Inputs: Units used = Miles and US gallons; Distance driven = 300; Fuel used = 10.
- Miles per US gallon 30.00
- Miles per UK gallon 36.03
- Liters per 100 km 7.84
- Kilometers per liter 12.75
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