Gas Mileage Calculator
Enter the distance and the fuel used on one trip, in miles and US gallons, miles and UK gallons, or kilometers and liters. Every mode shows the same trip as US MPG, UK MPG, kilometers per liter and liters per 100 km. Add the fuel price to see the cost per mile or km and per 100.
How to use the Gas Mileage Calculator
- Enter your numbers in the Gas Mileage Calculator above.
- Press the Calculate button to see the result.
- To try other numbers, change any value and press the button again.
The fuel efficiency formulas
MPG = Miles / Gallons · · · km/L = US MPG × 1.609344 / 3.785411784 = UK MPG × 1.609344 / 4.54609 · · · L/100 km = (Liters × 100) / km · · · US MPG = 100 × 3.785411784 / (1.609344 × L/100 km)
The conversions use 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L and 1 UK gallon = 4.54609 L. Higher MPG means less fuel for the distance, and so does a higher km/L or a lower L/100 km. Cost per mile or km is price × fuel ÷ distance, and cost per 100 is that times 100. Fuel economy and cost per 100 are rounded to two decimals, cost per mile or km to three.
Worked example
Drove 380 miles on 12.5 gallons: MPG = 380 / 12.5 = 30.4, shown as 30.40 mpg, which is 12.92 km per liter. At $3.50 a gallon the fuel cost $0.115 a mile, or $11.51 per 100 miles. In metric the same trip is about 611.6 km on 47.3 L, since 12.5 gal ≈ 47.3 L and 380 mi ≈ 611.6 km. Enter those and L/100 km = (47.3 × 100) / 611.6 ≈ 7.73, with an MPG equivalent of 30.41. That is a hundredth above 30.40 because 611.6 and 47.3 are rounded. In UK gallons, 380 miles on 10.4 gallons is 36.54 UK MPG, 12.93 km/L and 7.73 L/100 km, or 30.42 US MPG.
Frequently asked questions
What is the difference between UK and US MPG?
The gallon. NIST lists the UK gallon as 4.54609 liters and the US gallon as about 3.785 liters, so one mile per UK gallon is about 0.83 miles per US gallon. A car at 30.40 US MPG is at 36.51 UK MPG, on the same fuel. Pick the mode that matches the gallons you filled, and the result shows both.
How do I get km per liter?
Every mode shows it. Enter kilometers and liters in Metric, or miles and gallons in the other two. 611.6 km on 47.3 L is 12.93 km/L.
Why is a lower L/100 km better?
L/100 km counts the liters needed to cover 100 km, so fewer liters means less fuel for the same distance. MPG counts the distance covered on one gallon, so there a higher number is better. The calculator shows all of them for every trip.
What do the cost figures show?
What the fuel for this trip cost per mile or km and per 100 miles or km, at the price per gallon or liter you enter. Leave the price empty or at 0 and those two boxes show a dash.