How to use
- Enter the one-way distance in miles or kilometres. Round trip is on by default; switch it off for a one-way drive.
- Enter your fuel economy and pick its unit: mpg (US), mpg (UK), L/100 km or km/L.
- Enter the fuel price per US gallon or per litre. The trip cost, fuel needed and cost per mile or km appear instantly.
- Sharing the drive? Add the number of people to see each person’s share.
How it’s calculated
| Item | Calculation |
|---|---|
| Fuel needed | total distance ÷ fuel economy (converted to the same units) |
| Trip cost | fuel needed × price per gallon or litre |
| Cost per mile | price per gallon ÷ mpg |
| L/100 km → km/L | 100 ÷ (L/100 km) |
| mpg (US) → km/L | mpg × 1.609344 ÷ 3.785411784 |
| mpg (UK) → km/L | mpg × 1.609344 ÷ 4.54609 |
A mile is exactly 1.609344 km, a US gallon is exactly 3.785411784 litres and an imperial (UK) gallon is exactly 4.54609 litres — which is why the same car shows a higher mpg figure in the UK than in the US.
Examples
| Trip | Result |
|---|---|
| 250 miles each way, round trip, 30 mpg, 3.50 a gallon | 16.67 gallons, 58.33 total, about 0.117 a mile |
| Same trip split between 2 people | 29.17 each |
| 400 km one way at 6.5 L/100 km, 1.80 a litre | 26 litres, 46.80 |
A car that gets 25 mpg instead of 30 would use 20 gallons on the same round trip and cost 70.00 — about 20% more.
Things to keep in mind
- Results are for reference only. Real-world fuel economy depends on traffic, speed, air conditioning, cargo and tyre pressure, and is often lower than the rated figure. Your own fill-up records give the most accurate number.
- Fuel prices vary by region and station; use the price where you expect to fill up.
- Tolls, parking and wear on the car are not included.
- Need to convert miles and kilometres? Try the length converter. Paying for fuel abroad? The currency converter can help.
FAQ
How do I measure my real mpg?
Fill the tank, reset the trip meter, then at the next fill-up divide the miles driven by the gallons you put in. 360 miles on 12 gallons is 30 mpg.
Is a higher L/100 km better?
No — it is the fuel used per 100 km, so lower is better. 8 L/100 km equals 12.5 km/L, or about 29.4 mpg (US).
Is anything I enter saved or sent anywhere?
No. All calculations run in your browser.