Miles per Gallon, L/100 km, Trip Cost and Annual Fuel Use
Use odometer readings, direct trip distance or multiple fill-ups. Convert US MPG, Imperial MPG, km/L and L/100 km, then estimate cost per mile, trip cost and annual fuel spending.
Measurement method
Enter one fill-up per line as distance, fuel, total fuel cost. Example: 350,14,49.
Fuel price and planning
Fuel economy result
How to figure out mileage per gallon
Subtract the starting odometer from the ending odometer to get distance travelled, then divide miles by US gallons used. The same measured trip is converted into Imperial MPG, kilometres per litre and litres per 100 kilometres.
Why multiple fill-ups are better
Pump shutoff, parking angle and incomplete refills can distort one tank. Combining several fill-ups divides total distance by total fuel and reduces the effect of any one measurement.
What is the formula for MPG?
US MPG equals miles travelled divided by US gallons consumed.
Why is Imperial MPG higher than US MPG?
An Imperial gallon is larger than a US gallon, so the numerical MPG value is higher for the same vehicle and trip.
Calculate MPG from odometer readings, trip distance or multiple fill-ups
The miles per gallon calculator supports the full-tank method, a direct distance-and-fuel entry and multiple fill-up totals. It also converts US MPG to Imperial MPG, liters per 100 kilometers and kilometers per liter, then connects fuel economy to trip cost, cost per mile and annual fuel spending.
Most reliable full-tank method
Fill the tank, reset the trip meter or record the odometer, drive normally, then refill to a comparable level. Divide the miles driven by the US gallons added at the second fill. A single partial fill does not reveal how much fuel was actually consumed unless it is part of a longer multi-fill record bounded by full fills.
Odometer and direct-distance modes
Odometer mode subtracts the starting reading from the ending reading. Direct mode accepts a known trip distance. The selected distance and fuel units are converted before MPG is calculated, preventing an Imperial gallon or kilometer entry from being treated as a US-mile measurement.
Multiple fill-up average
A longer average reduces sensitivity to pump shutoff, slope, temperature and small refill differences. Add the distance and fuel from several complete intervals, then calculate total distance divided by total fuel. This is more meaningful than averaging individual MPG values when the intervals cover different distances.
Fuel cost and annual estimate
Enter fuel price to calculate trip cost and cost per mile. Annual distance projects annual fuel use and spending at the measured fuel economy. These are planning estimates: traffic, load, weather, tire pressure, route, idling and seasonal fuel blends can change future performance.
US MPG, Imperial MPG and L/100 km
US and Imperial gallons are not the same size, so their MPG values must not be compared directly. Liters per 100 kilometers is an inverse consumption measure: a lower number is better. Kilometers per liter is a distance-per-fuel measure: a higher number is better.
Fuel-economy troubleshooting
- Use complete fill-to-fill intervals.
- Verify distance and gallon units.
- Do not use the dashboard’s instantaneous MPG as the fuel-purchase calculation.
- Compare similar seasons and routes.
- Investigate a sustained change rather than one unusual tank.
How do I figure miles per gallon?
Divide miles driven by US gallons used. For 350 miles and 14 gallons, the result is 25 MPG.
Why does my calculated MPG differ from the dashboard?
The dashboard uses vehicle sensors and software estimates. A fill-to-fill result uses purchased fuel and odometer distance, but it can also vary because the tank may not be filled to exactly the same level.