Your vehicle’s real observed fuel economy, calculated directly from a trip’s odometer distance and fuel actually used.
How it works
Dividing miles driven by gallons of fuel used gives miles per gallon.
What this does not include
This does not include converting an already-known mpg figure to other units — for that, use this site’s fuel economy converter instead. This tool calculates mpg from a real trip’s numbers.
How to use this calculator
- Enter the miles driven and gallons of fuel used.
A worked example
300 miles driven on 10 gallons → 300 ÷ 10 = 30 mpg. 450 miles on 15 gallons → also 30 mpg — same rate, different trip length.
What the variables mean
| Variable | Meaning |
|---|---|
| Miles driven | Odometer distance since the last fill-up |
| Gallons used | Fuel needed to fill the tank back up |
Edge cases worth knowing
A partial fill-up understates gallons used, inflating the mpg result. This calculation assumes the tank was filled completely both times — topping off short leaves less fuel counted than was actually burned.
Highway and city driving produce genuinely different real mpg, not just different manufacturer ratings — steady highway speeds are typically more fuel-efficient than stop-and-go city driving.
Frequently asked questions
How do I track miles and gallons for this calculation?
Reset your trip odometer at a fill-up, then note the miles driven and gallons needed to fill up again — that gives you the numbers for this calculator.
Why might my calculated mpg differ from my car’s manufacturer rating?
Manufacturer ratings come from standardized testing conditions; real-world driving (traffic, terrain, driving style, weather) commonly produces different actual fuel economy.
Is this the same as the site’s fuel economy converter?
That one converts an already-known mpg figure between different units (like L/100km); this one calculates mpg itself from your actual trip data.
