Gas Mileage Calculator
Find your car's real gas mileage. Enter the miles you drove and the gallons it took to refill the tank to see your miles per gallon, the same figure in km/L and L/100 km, and your fuel cost per mile.
Miles per gallon (US)
28
Check the highlighted fields to see your result.
- Liters per 100 km
- 8.4
- Kilometers per liter
- 11.9
- MPG (UK gallons)
- 33.63
- Cost per mile
- —
Results are estimates for information only and do not constitute financial, medical, or legal advice.
How it works
Fuel economy is the distance you drive divided by the fuel you use. The calculator works it out in your units and converts it to the other common forms. L/100 km works the other way around: lower numbers mean better economy.
The formulas
MPG = miles ÷ gallons
L/100 km = 235.21 ÷ MPG · km/L = MPG × 0.4251
Worked example
You drove 350 miles and needed 12.5 gallons to refill the tank, at $3.50 a gallon.
- MPG: 350 ÷ 12.5 = 28 mpg.
- That's about 8.4 L/100 km or 11.9 km/L.
- Cost per mile: 12.5 × $3.50 ÷ 350 = $0.125.
Frequently asked questions
How do I measure my real gas mileage?
Fill the tank completely and reset the trip odometer. Drive normally until you need fuel, fill it completely again, and note how many gallons you added. Divide the miles on the trip odometer by those gallons. Repeating it over a few tanks gives a more reliable average.
Why is my mileage lower than the EPA rating?
Real mileage depends on speed, traffic, short trips, cold weather, air conditioning, tire pressure, and cargo. Highway speeds above about 50 mph also lower mileage quickly, because air resistance grows with speed.
What's the difference between US and UK mpg?
A UK (imperial) gallon is about 4.55 liters, while a US gallon is about 3.79 liters. The same car gets about 20% more "miles per gallon" in UK units, even though it uses the same amount of fuel.