Gas Mileage Calculator · Practical guide
How to Calculate MPG
Miles driven divided by gallons used is all it takes to find your real fuel economy.
At a glance
The MPG Formula
To calculate MPG, divide the miles you drove by the gallons of gas you used. If you drove 300 miles and burned 10 gallons, your fuel economy is 300 ÷ 10 = 30 MPG. The calculator above does this instantly and also converts the result to L/100km.
Interactive tool
Gas Mileage Calculator
Enter your own values, then compare the result with the examples below.
Mileage Results
Using the Fill-Up Method
For the most accurate number, fill your tank completely and reset your trip odometer. At your next fill-up, note the miles on the trip odometer and the gallons it takes to fill the tank again. Divide the two and you have your true real-world MPG for that tank, not the sticker estimate.
Worked Example
Say your trip odometer reads 312 miles and the pump stops at 11.7 gallons. Your MPG is 312 ÷ 11.7 = 26.7 MPG, which converts to about 8.8 L/100km. Repeat this over a few tanks and average the results to smooth out differences between highway and city driving.
Common MPG Reference Points
| MPG | L/100km | Typical Vehicle |
|---|---|---|
| 20 | 11.8 | Large SUV or truck |
| 25 | 9.4 | Midsize SUV |
| 30 | 7.8 | Compact sedan |
| 40 | 5.9 | Hybrid |
Frequently Asked Questions
Is MPG calculated the same for city and highway driving?
The formula is the same, but your results will differ. City driving with stops and idling usually returns fewer miles per gallon than steady highway cruising.
Why is my calculated MPG lower than the EPA rating?
EPA ratings come from controlled lab tests. Real-world factors like traffic, terrain, weather, cargo weight, and driving style usually lower your actual mileage.
How many tanks should I measure for a reliable average?
Three to five tanks is a good baseline. That covers a mix of driving conditions and evens out fill-up inconsistencies.
Does the calculator work with kilometers and liters?
Yes. Switch the unit system to kilometers and liters and it will compute L/100km directly, plus the MPG equivalent.