What is my gas mileage?
Fill the tank, note the odometer, and at the next fill-up enter the distance driven and the fuel it took. See your gas mileage in mpg and L/100 km.
- Miles per gallon
- 30
300 mi on 10 gal is 30 mpg, or 7.84 L/100 km.
- Liters per 100 km
- 7.84
- Kilometers per liter
- 12.75
- Miles per UK gallon
- 36.03
- Gallons per 100 miles
- 3.33
Miles per gallon: 30. 300 mi on 10 gal is 30 mpg, or 7.84 L/100 km.
How to calculate
Works out a car’s gas mileage from the distance driven and the fuel used, in miles per gallon (US and UK), liters per 100 km, km per liter, and gallons per 100 miles.
Example with the default inputs (Distance driven 300 mi, Fuel used 10 gal): 300 mi on 10 gal is 30 mpg, or 7.84 L/100 km.
Method: mpg = miles driven ÷ gallons used; L/100 km = liters used ÷ kilometers driven × 100
- Fill the tank completely both times, so the fuel you add equals the fuel used since the last fill.
- A US gallon is 3.785411784 L, a UK gallon 4.54609 L, and a mile 1.609344 km, all exact.
- Results are exact from the typed numbers and show to 2 decimal places, rounded half up.
Worked examples
Each example is checked against the calculator on every build.
- Distance driven 356.2 mi, Fuel used 13.5 gal gives Miles per gallon 26.385185, Liters per 100 km 8.914646, Gallons per 100 miles 3.790006.Source: Fueleconomy.gov, Calculating Your MPG: 356.2 miles ÷ 13.5 gallons = 26.4 mpg (https://fueleconomy.gov/mpg/MPG.do?action=calcMPG)
- Distance driven 300 mi, Fuel used 10 gal gives Miles per gallon 30, Liters per 100 km 7.840486, Kilometers per liter 12.754311, Miles per UK gallon 36.028498.Source: NIST SP 811 (2008), Appendix B: 1 gal = 3.785411784 L and 1 mi = 1.609344 km exactly
- Distance driven 310.7 mi, Fuel used 10.57 gal gives Liters per 100 km 8, Kilometers per liter 12.5, Miles per gallon 29.401823.Source: NIST SP 811 (2008), Appendix B
How it works
Type the distance in miles or kilometers (at least 1 meter) and the fuel in US gallons or liters (at least 1 mL). Every unit converts exactly: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L, and 1 UK gallon = 4.54609 L.
- Miles per gallon = miles ÷ US gallons.
- Liters per 100 km = liters ÷ kilometers × 100.
- Kilometers per liter = kilometers ÷ liters.
- Miles per UK gallon = miles ÷ UK gallons.
- Gallons per 100 miles = US gallons ÷ miles × 100.
Each result is worked out exactly from the typed numbers (the page reads each one to 15 significant figures after converting it to meters or cubic meters, which keeps every value typed with up to 5 digits exact) and shows to 2 decimal places, rounded half up from that exact value (12.345 shows as 12.35, 12.344999 as 12.34). mpg × L/100 km is always 235.2146 (100 × 3.785411784 ÷ 1.609344), so each converts to the other.
Worked examples by hand
356.2 miles on 13.5 gallons (the fueleconomy.gov example). 356.2 ÷ 13.5 = 26.39 mpg. In liters and kilometers: 13.5 × 3.785411784 = 51.1031 L and 356.2 × 1.609344 = 573.2483 km, so 51.1031 ÷ 573.2483 × 100 = 8.91 L/100 km. Gallons per 100 miles: 13.5 ÷ 356.2 × 100 = 3.79.
300 miles on 10 gallons. 300 ÷ 10 = 30 mpg. 235.2146 ÷ 30 = 7.84 L/100 km. 482.8032 km ÷ 37.8541 L = 12.75 km/L. In UK gallons, 10 × 3.785411784 ÷ 4.54609 = 8.3267, so 300 ÷ 8.3267 = 36.03 UK mpg.
500 km on 40 liters. 40 ÷ 500 × 100 = 8 L/100 km, and 500 ÷ 40 = 12.5 km/L. In US units, 235.2146 ÷ 8 = 29.40 mpg.
Other questions people ask
How do I calculate my gas mileage?
Fill the tank and note the odometer. At the next fill-up, note the odometer again and the gallons it took to fill the tank. Divide the miles driven by the gallons. fueleconomy.gov’s example: 356.2 miles ÷ 13.5 gallons = 26.4 mpg.
How do I convert mpg to L/100 km?
Divide 235.215 by the mpg. 30 mpg is 235.215 ÷ 30 = 7.84 L/100 km. The same number converts back: 235.215 ÷ 7.84 = 30 mpg. It comes from 100 × 3.785411784 L per gallon ÷ 1.609344 km per mile.
Why is L/100 km better when it is lower?
mpg measures distance per fuel, so higher is better; L/100 km measures fuel per distance, so lower is better. Fuel per distance also shows savings directly: going from 10 to 8 L/100 km saves 2 liters every 100 km.
Why is UK mpg higher than US mpg?
A UK (imperial) gallon is 4.54609 liters and a US gallon 3.785411784 liters, so a car goes further on a UK gallon. 30 US mpg is 36.03 UK mpg.
Why is my mpg lower than the EPA rating?
EPA ratings come from set laboratory test cycles. Short trips, high speed, cold weather, air conditioning, heavy loads and hard acceleration all use more fuel, so real mileage often differs from the label.
What does gallons per 100 miles mean?
It is the fuel used to drive 100 miles, shown on the EPA fuel economy label. 30 mpg is 100 ÷ 30 = 3.33 gallons per 100 miles.