Free fuel economy tool
MPG Calculator — Miles Per Gallon & Fuel Economy
Calculate your real-world MPG from fill-ups, convert between MPG / L/100km / km/L, and see how your car stacks up.
Calculate Your Real MPG
From your last fill-up — the honest number.
How to Calculate MPG
MPG = miles driven ÷ gallons used. Fill up, reset the trip odometer, drive normally, refill to the same pump click-off, then divide. That’s it — no app or OBD dongle needed, and it’s more honest than the dashboard readout (which typically flatters by 5–10%).
What’s Good MPG in 2026?
- Under 20 MPG: thirsty — trucks, large SUVs, performance cars.
- 20–30 MPG: average for gas cars and crossovers.
- 30–40 MPG: good — efficient sedans and most hybrids.
- 40+ MPG: excellent — hybrids and plug-in hybrids.
Biggest MPG Killers
- Aggressive driving (hard acceleration/braking): −15–30%.
- Under-inflated tires: −3–5%. Roof cargo box: −10–25% at highway speed.
- Short cold-start trips: the engine runs rich until warm.
- Excess weight: every 100 lbs ≈ −1% MPG.
Frequently Asked Questions
How do I calculate my car’s MPG?
Divide miles driven by gallons used to refill: 320 miles ÷ 11.5 gallons = 27.8 MPG. Average 3+ fill-ups for accuracy.
Why is my real MPG lower than the sticker?
EPA tests are lab-based and optimistic. Real-world driving — cold starts, AC, hills, traffic — typically runs 10–20% below the sticker.
How do I convert MPG to L/100km?
Divide 235.21 by MPG: 30 MPG = 7.84 L/100km. Note lower L/100km is better (it’s consumption, not economy).
Does premium gas improve MPG?
Only if your engine requires it (high compression/turbo). In a regular-grade engine, premium adds cost with zero MPG benefit.
What driving habits save the most fuel?
Gentle acceleration, steady speed, coasting to stops, and observing speed limits — smooth driving alone can improve MPG 15–30%.
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