How to budget fuel for a road trip

Fuel is often the biggest variable cost of a road trip. With the distance, your vehicle's fuel economy and the local price, you can estimate it in a minute.

Metric: litres per 100 km

Fuel cost = distance (km) ÷ 100 × L/100 km × price per litre

An 800 km trip in a car using 8.5 L/100 km is 68 litres. At 1.55 per litre that is 105.40, or 210.80 for the return trip.

Imperial: miles per gallon

Fuel cost = distance (miles) ÷ MPG × price per gallon

500 miles at 28 MPG uses about 17.9 gallons. At 3.50 per gallon that is about 62.50. US and Imperial gallons differ: an Imperial gallon is about 20% larger, so Imperial MPG figures look higher for the same car.

Converting economy figures

30 US MPG is about 7.8 L/100 km.

Make the estimate realistic

• Highway driving with a loaded car, roof box or trailer uses more fuel than the official rating.
• Winter driving and air conditioning increase consumption.
• Prices vary along the route; use an average or a slightly higher figure.
• Add a margin of 10% for detours and city driving.

Splitting the cost

Divide the total by the number of people sharing. The fuel cost calculator handles km or miles, both MPG types, return trips and splitting automatically. Driving electric? Try the EV charging cost calculator.

Reviewed October 2026 · How we build our calculators · Report an issue