Fuel Cost Calculator
Estimate fuel and trip costs using the units you drive with. Include a return journey and split the cost between travelers.
Your trip details
Your result
Enter your values, then choose Calculate.
Budget estimate using your inputs, not live fuel prices. Currency labels do not convert money.
How this calculator works
Select the unit system before entering your trip. For the United States, use miles, US miles per gallon and a price per US gallon. For a typical UK trip, use miles, Imperial MPG and a price per litre. Metric options support either litres per 100 kilometres or kilometres per litre.
UK: fuel cost = miles ÷ UK MPG × 4.54609 × price per litre
Metric: fuel cost = kilometres × L/100 km ÷ 100 × price per litre
km/L: fuel cost = kilometres ÷ km/L × price per litre
Example: a 300-mile trip
At 30 US MPG and $3.50 per US gallon, a 300-mile journey uses 10 US gallons and costs $35 in fuel. Add $10 in total tolls and parking to get $45. Split between two people, that is $22.50 each. The example button fills these inputs.
Example: metric and UK trips
A 400 km trip at 7 L/100 km consumes 28 litres. At 1.80 per litre, the fuel cost is 50.40 in your selected currency. For 100 miles at 40 UK MPG, fuel needed is 2.5 Imperial gallons, or about 11.37 litres. At £1.50 per litre, that is about £17.05.
US and UK gallons are different
A US gallon is approximately 3.78541 litres, while an Imperial gallon is 4.54609 litres. Using UK MPG with a US gallon calculation understates the fuel volume. This calculator keeps those conversions separate.
Make the budget useful
Use your vehicle’s measured economy for a similar journey if available, rather than assuming the best advertised figure. Enter your own current fuel price. For a return journey the distance doubles, but tolls and parking remain the whole-trip amount you entered.
The estimate excludes vehicle wear, depreciation, insurance and other costs not entered. For a journey with substantially different fuel prices or driving conditions, calculate the legs separately and add their costs.
Frequently asked questions
Does the return-trip option double everything?
It doubles the driving distance and therefore fuel use. Tolls and parking are a total-trip input and are not doubled.
Does changing the currency convert prices?
No. It changes only the display label. Enter fuel prices and extras in the same selected currency.
Why does the UK option ask for a litre price?
UK fuel economy is commonly expressed in Imperial MPG while pump prices are per litre. The calculation converts Imperial gallons to litres before applying that price.
Does the calculator include current pump prices?
No. You supply the price. There is no live fuel-price feed, and actual consumption can differ from the economy you enter.
Sources and review
Rules and methodology checked on 9 October 2026. Worked examples are illustrative calculations, not user testimonials.