How do I calculate gas mileage accurately?

Fill the tank, record the odometer, drive normally, refill, then enter the two readings and the fuel needed for the refill.

What units are available?

U.S. mode reports mpg with L/100 km and km/L conversions. Metric mode reports km/L, L/100 km, and mpg.

No. Leave it blank to calculate mileage only. When supplied, the calculator adds fill expense and cost per mile or kilometer.

The traveled distance is the current reading minus the previous reading, so a non-positive difference cannot represent the trip.

⌘K

Calculate MPG, km/L, L/100 km, distance traveled, fill expense, and fuel cost per distance from odometer readings.

Gas Mileage

24 mpg

Estimated result

Calculate fuel economy from two odometer readings and the fuel added at the second fill. Optional fuel price adds fill cost and unit-cost results.

In U.S. units, mpg = miles traveled / gallons. In metric units, km/L = kilometers traveled / liters and L/100 km = 100 / (km/L).

U.S. default

Driving 360 miles on 15 gallons gives 24 mpg, or 9.8 L/100 km. At $3 per gallon, the fill costs $45 and fuel costs $0.125 per mile.

How do I calculate gas mileage accurately?: Fill the tank, record the odometer, drive normally, refill, then enter the two readings and the fuel needed for the refill.
What units are available?: U.S. mode reports mpg with L/100 km and km/L conversions. Metric mode reports km/L, L/100 km, and mpg.
Is fuel price required?: No. Leave it blank to calculate mileage only. When supplied, the calculator adds fill expense and cost per mile or kilometer.
Why must the current odometer be larger?: The traveled distance is the current reading minus the previous reading, so a non-positive difference cannot represent the trip.