Fuel Cost Calculator
What will that road trip cost in fuel?
Fuel is often the biggest variable cost of a road trip — this estimator turns "about 300 miles" into a dollar figure.
How to use
- Pick imperial or metric units.
- Enter trip distance, your car’s efficiency and local fuel price.
- Get the trip cost and fuel needed instantly.
About this tool
Your car’s real-world efficiency is usually 10–20% worse than the sticker rating; adjust for city driving and loads.
All calculations stay in your browser.
How it works
Fuel cost comes from two multiplications. First the fuel used: in the US, gallons = miles / mpg; in metric, liters = km x (L/100km) / 100. Then cost = fuel used x price per unit.
MPG and L/100km are inverses of each other — one is distance per fuel, the other fuel per distance — so convert with 235.2 / mpg = L/100km. Your real-world efficiency is usually 10-20% worse than the official rating.
If you do not know your car's efficiency, measure it: fill the tank, reset the trip meter, drive normally, then refill and divide miles driven by gallons added. Two or three fill-ups give a far more honest number than the dashboard estimate.
Worked examples
300-mile trip at 30 mpg, $3.50/gal: Fuel: 300 / 30 = 10 gallons. Cost: 10 x 3.50 = $35.00.
500 km at 8 L/100km, $1.50/L: Fuel: 500 x 8 / 100 = 40 liters. Cost: 40 x 1.50 = $60.00.
Quick reference
| MPG | L/100km |
|---|---|
| 20 | 11.8 |
| 25 | 9.4 |
| 30 | 7.8 |
| 40 | 5.9 |
Frequently asked questions
How do I find my car’s MPG?
Divide miles driven by gallons used between fill-ups, or check your dashboard trip computer.
Why L/100km instead of km/L?
Lower is better with L/100km (fuel per distance), which makes comparisons intuitive.
Is my data uploaded?
No — everything is local.
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