A walkthrough, end to end.
- 1
Enter the distance traveled and the fuel used.
- 2
Pick the units (miles + gallons or km + litres).
- 3
See MPG, L/100km, and km/L all at once.
Fuel economy
MPG = miles / gallons. L/100km = (litres × 100) / km. km/L = km / litres.
What you can do with this.
Track your real MPG
Compute actual fuel economy after a fill-up.
Cross-country trip review
Average MPG over a long trip.
Compare to EPA estimate
See if you match window-sticker numbers.
International conversion
Convert from MPG to L/100km for European cars.
Driver coaching
Track changes in fuel economy with driving habits.
Fleet tracking
Per-trip mileage for company vehicles.
Fuel-up logging
Add a manual entry to your records.
MPG 2026 — what's current
Modern cars include onboard MPG; calculator wins for cross-system conversion.
Frequently asked.
MPG mode uses US gallons (3.785 L). UK MPG uses UK gallons (4.546 L) — multiply US MPG by 1.201.
Yes — enter the distance and gallons since the last fill-up.
No. All math runs in your browser.
Use kWh instead of gallons; the calculator shows distance per energy unit.