How MPG Calculator Works?
This tool works by dividing the miles you traveled by the gallons of fuel you used. The result is your real-world fuel economy in miles per gallon (MPG).
Fill the tank completely
Fill up until the pump clicks off, then reset the trip meter to 0. A full tank sets a fixed starting point.
Drive normally
Drive your usual mix of city and highway roads. Aim for at least 200 miles (322 km) so the reading reflects typical driving.
Refill and note the gallons
Fill the tank to the click again and write down the gallons pumped. The pump display shows the figure to 3 decimals.
Enter both numbers
Type the trip meter miles and the gallons into the calculator. The MPG result appears instantly.
MPG Calculator Formula
The formula is MPG = Miles Traveled ÷ Gallons Consumed. The formula is the official definition of fuel economy in the United States.
MPG = Miles Traveled ÷ Gallons ConsumedFormula variables
- Miles Traveled
- Distance shown on the trip meter between 2 fill-ups.
- Gallons Consumed
- US gallons pumped to refill the tank. 1 US gallon equals 3.785 liters.
Worked example
- Miles Traveled: 360 miles
- Gallons Consumed: 12 gallons
- Take 360 miles (579 km) from the trip meter.
- Divide by 12 gallons (45.4 liters): 360 ÷ 12 = 30.00 MPG.
Result: 30.00 (MPG)
A result of 30 MPG equals 7.84 liters per 100 kilometers (L/100km) and 12.75 kilometers per liter (km/L). Averaging 3 or more tank readings smooths out small pump and trip meter errors.
MPG Calculator Conversion Table
The table shows MPG results for 5 trip distances and 4 fuel amounts. Find your miles on the left and your gallons along the top.
Rows: Miles Traveled (miles). Columns: Gallons Consumed (gallons). Cells: MPG.
| miles | 8 gallons | 10 gallons | 12 gallons | 15 gallons |
|---|---|---|---|---|
| 200 miles | 25.00 | 20.00 | 16.67 | 13.33 |
| 300 miles | 37.50 | 30.00 | 25.00 | 20.00 |
| 360 miles | 45.00 | 36.00 | 30.00 | 24.00 |
| 400 miles | 50.00 | 40.00 | 33.33 | 26.67 |
| 500 miles | 62.50 | 50.00 | 41.67 | 33.33 |
A 400-mile tank on 10 gallons returns 40 MPG, while the same 400 miles on 15 gallons returns 26.67 MPG. Fewer gallons for the same distance means better fuel economy.
What is MPG Calculator?
The MPG Calculator is a tool that measures the real fuel economy of your vehicle from miles driven and gallons pumped. The calculator gives the number your car achieves, not the number printed on the sticker.
Real MPG differs from the EPA rating by 5% to 20% for most drivers. Speed, climate, tire pressure, and cargo weight shift the result, so a measured figure gives better cost estimates than a lab figure.
The tool needs 2 inputs and returns 1 output. Track the result every fill-up to spot a sudden drop of 10% or more, which points to low tire pressure, a dirty air filter, or a failing oxygen sensor.
What are the uses of MPG Calculator?
There are 5 main uses of the MPG Calculator: tracking fuel economy, spotting mechanical problems, testing driving habits, verifying sticker ratings, and feeding cost calculators.
Tracking fuel economy
Owners record MPG at each fill-up to build a history of how the vehicle performs across seasons.
Spotting mechanical problems
A drop from 30 MPG to 25 MPG in a single month signals a maintenance issue worth checking.
Testing driving habits
Drivers compare MPG at 65 mph against 75 mph to see the fuel cost of higher highway speeds.
Verifying sticker ratings
Buyers check whether a used car matches its EPA combined rating before trusting it for long trips.
Feeding cost calculators
A measured MPG gives trip, commute, and annual fuel cost tools a more accurate starting value.
Need every metric in one place? Open the main MPG Cost Calculator or browse all 101 fuel calculators.