How to use
- Enter the trip distance in kilometres or miles.
- Enter your car’s fuel economy and pick its unit: L/100 km, km/L, or mpg in US or UK gallons.
- Enter the fuel price per litre, US gallon or UK gallon.
- Choose round trip if you are coming back, and the number of people sharing the cost.
Fuel cost formula
fuel used = distance ÷ fuel economy
cost = fuel used × price per litre or gallon
- With L/100 km: fuel used = distance (km) × L/100 km ÷ 100.
- Units are converted first, so you can mix miles, litres and UK mpg.
- This is the same idea as the US EPA label’s annual fuel cost: fuel price ÷ mpg × miles.
Examples
- 300 miles at 30 mpg (US), 3.50 a gallon: 300 ÷ 30 = 10 gallons, costing 35.00.
- 500 km at 7 L/100 km, 1.80 a litre: 500 × 7 ÷ 100 = 35 litres, costing 63.00.
- Splitting it: a 150-mile trip each way at 30 mpg and 3.50 a gallon costs 35.00 for the round trip, or 17.50 each for two people.
Fuel economy equivalents
| mpg (US) | mpg (UK) | L/100 km | km/L |
|---|---|---|---|
| 20 | 24.0 | 11.8 | 8.5 |
| 25 | 30.0 | 9.4 | 10.6 |
| 30 | 36.0 | 7.8 | 12.8 |
| 40 | 48.0 | 5.9 | 17.0 |
| 50 | 60.0 | 4.7 | 21.3 |
A UK gallon (4.546 L) is bigger than a US gallon (3.785 L), so UK mpg figures are about 20% higher for the same car. For other values, use the fuel economy converter.
Why your real cost may differ
Official and dashboard figures are measured in set conditions. High speed, stop-start traffic, hills, air conditioning, roof boxes, heavy loads and cold weather all raise fuel use.
For an electric car, the electricity cost calculator works out charging cost from kWh and your price per kWh.