Travel
How to Calculate Fuel Costs
Estimate what a journey costs in fuel, whether to use litres per 100 km or miles per gallon, and how to split the cost between passengers.
4 min read
The core calculation
Work out the fuel you will use, then multiply by the pump price.
- Fuel needed = (distance ÷ 100) × consumption in L/100 km
- Cost = fuel needed × price per litre
- Example: 450 km at 8 L/100 km uses 36 litres; at 1.60 per litre that is 57.60
If you know MPG instead
Miles per gallon measures efficiency in the opposite direction: higher is better. Convert before calculating.
- km per litre = MPG (US) × 0.4251
- L/100 km = 235.215 ÷ MPG (US)
- Example: 35 MPG is about 6.72 L/100 km
| L/100 km | MPG (US) | MPG (UK) |
|---|---|---|
| 4.0 | 58.8 | 70.6 |
| 6.0 | 39.2 | 47.1 |
| 8.0 | 29.4 | 35.3 |
| 10.0 | 23.5 | 28.2 |
| 12.0 | 19.6 | 23.5 |
Real-world adjustments
Manufacturer consumption figures come from standardised tests. Real driving usually uses more fuel.
- Urban driving with stopping and starting can add 20–40%.
- Roof boxes, open windows and under-inflated tyres all increase drag.
- Carrying weight matters most for acceleration, less for steady cruising.
- Air conditioning typically adds 5–10% in town.
- Check consumption when the tank is brimmed, not from the trip computer alone.
Splitting the cost
Divide the fuel cost by the number of people travelling. Whether the driver should also charge for wear and tear is a matter for the group — a common approach is to add a fixed rate per kilometre for maintenance and depreciation.
Do it automatically
Skip the arithmetic — the VELNARO Fuel Cost Calculator works it out instantly and shows the working.
Open the Fuel Cost CalculatorMore tools in calculators.