Distance conversion
Miles are converted to kilometres with 1 mi = 1.609344 km before fuel use is calculated.
Interactive Tool
Road Trip Fuel Cost Calculator
Enter your distance, vehicle fuel economy and local fuel price to estimate litres used, total cost and cost per 100 km.
A clear estimate for the fuel part of your trip
The calculator converts every input to kilometres, litres and a price per litre before calculating the result. Choose US mpg and US gallons or UK mpg and UK gallons when those are the units shown by your vehicle or fuel station.
The currency selector formats the result but does not fetch exchange rates or live fuel prices. Use a current local price and treat the estimate as a planning figure: traffic, hills, weather, passengers and driving style can change real consumption.
Fuel economy conversion
US mpg becomes 235.215 ÷ mpg in L/100 km. UK mpg uses 282.481 ÷ mpg because an Imperial gallon is larger.
Cost calculation
Fuel used = kilometres × L/100 km ÷ 100. Total cost = litres used × price per litre.
Sources and method
The conversion constants and fuel-economy context are based on these public technical references:
- NIST Guide to the SI, Appendix B NIST gives the 235.215 US mpg to L/100 km relationship and the mile-to-kilometre factor used here.
- NIST Guide to the SI, Appendix B.9 NIST lists 1 US gallon = 3.785412 litres and 1 UK Imperial gallon = 4.54609 litres.
- US EPA Fuel Economy EPA explains official vehicle fuel-economy estimates and provides fuel-economy data for comparison.
Fuel cost calculator questions
Why are US mpg and UK mpg separate options?
A US gallon and a UK Imperial gallon hold different volumes, so the same mpg number does not describe the same fuel consumption. Select the unit used by your vehicle or source.
Does the calculator convert currencies?
No. Currency selection formats the result only. It does not apply an exchange rate, so enter the fuel price in the currency selected for the calculation.
What does cost per 100 km show?
It expresses the estimated fuel cost for each 100 kilometres after your distance, economy and price inputs are converted. It helps compare trip budgets using different distances.
Why can the actual cost be different?
The estimate uses the fuel economy and price you enter. Traffic, speed, terrain, weather, vehicle load, idling and changes at the pump can all change the real amount used or paid.
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Verify the result before you rely on it
Check destination-specific rules and compare a related planner. Tool outputs are planning aids, not official permission or live route data.