How to use the trip fuel cost calculator
- Choose your units at the top: US (miles, US MPG, price per gallon), UK (miles, UK MPG, price per litre) or metric (kilometres with L/100 km or km/L).
- Enter the one-way distance from a map app and tick round trip if you are driving back.
- Enter your car’s real fuel economy. The trip computer or your last few fill-ups are better guides than the official rating.
- Check the fuel price. The US, eurozone and Australian fields start with a published average; use the price at your usual station instead if you know it.
- Enter the number of people sharing the cost to see each person’s share.
How the cost is worked out
Metric: fuel (L) = distance (km) × L/100 km ÷ 100, or distance ÷ km/L
Cost per person = cost ÷ people
Internally every figure is converted to kilometres and litres per 100 km, so all four unit choices give the same answer for the same trip. A UK gallon is 4.546 litres and a US gallon 3.785 litres, which is why UK MPG figures look higher for the same car.
Worked example
A 300 mile one-way trip in a car that averages 28 MPG, with regular gasoline at $4.354 a gallon (the EIA US average for the week of October 5, 2026), driven alone:
- Fuel used: 300 ÷ 28 = 10.71 gal.
- Cost: 10.714 × $4.354 = $46.65 for 300 mi.
- That works out at $0.16 per mi. Ticking round trip doubles it, and splitting between three people divides it by three.
Tips for a more accurate trip budget
- Motorway speed costs fuel. Most cars use noticeably more fuel at high speed than at a steady moderate pace, so long fast trips often fall short of the rated economy.
- Load and roof boxes matter. Passengers, luggage, roof boxes and bike racks all add weight or drag.
- Check tyre pressures. Under-inflated tyres raise fuel use and wear the tyres faster.
- Add the extras separately. Tolls, parking, ferries and congestion charges are not fuel, but they belong in the trip budget too.
- Prices vary along the route. Motorway service stations are usually dearer than supermarket or town stations.
US, UK and Canada differences
US drivers measure in miles and US gallons, and the price preset is the EIA weekly average for regular gasoline. UK drivers buy fuel by the litre but usually quote economy in miles per imperial gallon, so the UK option combines miles, UK MPG and a price per litre. Canada sells fuel by the litre and its official ratings use L/100 km, although many Canadians still think in miles per gallon; pick whichever matches the number you have.
Metric units and other countries
In most of Europe, fuel use is given in litres per 100 km. In Pakistan, India, Japan and some other countries, kilometres per litre is the everyday unit, so the km/L option is there for them. Outside the regions with a preset price, type today’s pump price per litre in your currency.