Gas Mileage Calculator
Your car’s real fuel economy from a fill-up or several, in mpg, km/L and L/100 km at once, with the cost per mile or km if you add the fuel price.
Result
Fuel economy: 30.97 mpg
Fill to the same point each time: the pump’s first click-off is the usual mark.
- Miles per gallon, US and imperial
- 30.97 mpg (37.19 mpg (imp))
- Kilometres per litre
- 13.17 km/L
- Litres per 100 km
- 7.6 L/100 km
- Distance measured
- 384 mi
https://calcgallery.com/running-costs/gas-mileage-calculator/
Results are arithmetic on the figures you enter. The site stores no vehicle data, fuel prices, mileage rates, depreciation rates or residual values, because they vary by model and place and change over time. Real fuel economy varies with driving, weather and load. Nothing here is a fitment, safety or financial recommendation. Read the full disclaimer
How to use the Gas Mileage Calculator
- For one fill-up, fill the tank, drive, fill it again, and enter the distance and the fuel it took.
- For a better figure, use several fill-ups, entering the odometer at the first and last and the fuel added at every fill after the first.
- Read the economy in mpg, km/L and L/100 km, and optionally the fuel cost per mile or km.
The formula
economy = distance ÷ fuelWith several fill-ups, the distance is the last odometer reading minus the first, and the fuel is everything added after the first fill. The result is converted exactly into all three common forms: US and imperial miles per gallon, kilometres per litre, and litres per 100 km.
One number, three scales
A US gallon is 3.785 litres and an imperial gallon 4.546, so the same car is about 20% more mpg in the UK than in the US. Litres per 100 km has no gallon to argue about and, because it measures fuel used, it adds up directly: a car at 7.84 L/100 km uses 78.4 litres over 1,000 km.
Cost per mile
Enter a fuel price to see what each mile or kilometre costs in fuel. Take it to the fuel cost calculator to price a whole trip.
With your numbers
- Distance 384 mi ÷ fuel 12.4 gal
- = 30.97 mpg = 7.6 L/100 km
Quick reference
Fill to the same point each time: the pump’s first click-off is the usual mark.
| Example | Fuel economy |
|---|---|
| 384 mi on 12.4 gallons | 30.97 mpg |
| 620 km on 46 litres | 7.42 L/100 km |
| 300 mi on 10 gallons | 30 mpg |
| 10,000 to 11,050 on 35.5 gallons | 29.58 mpg |
| With fuel at 3.459 a gallon | 30.97 mpg |
| 500 km on 30 litres | 6 L/100 km |
Common questions about the Gas Mileage Calculator
- Why is the first fill-up left out?
- Because the fuel from that fill was burned before you started counting miles. Fill up, note the odometer, then add up only the fuel at the later fills. Driving 1,050 miles on fills of 11.2, 12.8 and 11.5 gallons after the first is 35.5 gallons and 29.58 mpg. Counting the first fill too, say another 11.2, gives 22.48 mpg, which is wrong.
- How accurate is one fill-up?
- Roughly. Pumps shut off at slightly different levels, so a single tank can be a few percent out either way. Several fill-ups spread that error over more miles.
- Why do mpg and L/100 km run in opposite directions?
- mpg is distance per fuel, so a bigger number is better. L/100 km is fuel per distance, so a smaller number is better. A car improving from 20 to 30 mpg saves far more fuel than one improving from 40 to 50, which is easier to see in L/100 km: 11.76 to 7.84 against 5.88 to 4.70.
- Why is my figure worse than the rating?
- Ratings come from standard laboratory test cycles. Short trips, cold engines, high speeds, air conditioning, roof racks and heavy loads all use more fuel than the test does.