--- title: "Road Trip Fuel Cost Calculator, Miles or Km | Quiet Detour" description: "Work out a road trip's fuel cost in miles or km: any mpg or L/100 km, price per gallon or litre, one way or round trip, split between everyone in the car." url: https://quietdetour.me/ --- Miles or kilometres · US or UK gallons · litres # Road trip fuel cost calculator How much fuel will the drive take, and what will it cost each of you? Enter the distance, your car's fuel economy and the price at the pump. ## How the cost is worked out The calculator turns your distance into kilometres and your fuel economy into litres per 100 km, works out the litres the trip needs, and multiplies by the price per litre. A round trip doubles the distance. The fuel is shown in litres and in US and UK gallons, because the two gallons differ: a US gallon is 3.785 litres and a UK (imperial) gallon 4.546 litres, so 30 mpg in UK gallons is only about 25 mpg in US gallons. Use the fuel economy you really get on similar roads; your car's trip computer is a better guide than the brochure. Prices work in any currency, and the cost comes out in the currency you typed the price in. ## Sources - US gallon: 231 cubic inches, from [NIST Handbook 44](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition), Appendix C. With the inch defined as exactly 2.54 cm, that is exactly 3.785411784 litres. - UK (imperial) gallon: exactly 4.54609 litres, from the [Weights and Measures Act 1985, Schedule 1](https://www.legislation.gov.uk/ukpga/1985/72/schedule/1). - Mile: exactly 1.609344 km, and the inch and imperial gallon factors, from [NIST Special Publication 811, Appendix B.8](https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8). ## More calculators for the road Plan the time, the stops and the fun, as well as the fuel. - [Fuel economy converter](https://quietdetour.me/fuel-economy-converter/): mpg (US), mpg (UK), L/100 km and km/L, with the mpg illusion explained. - [Drive time calculator](https://quietdetour.me/drive-time-calculator/): Arrival time and a stop-by-stop plan with a rest break every two hours. - [Scenic detour calculator](https://quietdetour.me/detour-calculator/): What the long way round adds in miles, minutes, fuel and money. - [EV charging calculator](https://quietdetour.me/ev-charging-calculator/): Charging time and cost for one charge, or the charging stops for a trip. - [Road trip bingo](https://quietdetour.me/road-trip-bingo/): Printable bingo cards of things to spot from the car, for the back seat. ## Recommended Two free services that help with the online side of a trip. Temporary email · no sign-up ### CleanTempMail Motorway services, roadside cafés and motels often want an email address before the Wi-Fi works, and the offers keep coming long after the trip. CleanTempMail gives you a free temporary inbox straight away: no sign-up, a random or custom address on hundreds of domains, and messages deleted automatically after 3 days. [Get a temporary inbox](https://cleantempmail.com/) Disposable cloud browser · domain lookups ### WebTraceCheck Found a cabin, campsite or motel on a site you have never heard of? WebTraceCheck's free DNS and domain lookup shows how old a site's domain is, and its disposable cloud browser opens unfamiliar links on an isolated desktop that is deleted after each session. Nothing to install, with free time every day. [Try WebTraceCheck](https://webtracecheck.com/) ## Questions **Should I use US or UK gallons?** Use the gallon your figures are quoted in. US fuel economy figures and US pump prices use the US gallon of 3.785 litres; UK mpg figures use the imperial gallon of 4.546 litres. Mixing the two is an easy mistake, so the calculator lets you choose the unit of each figure separately. **Does a round trip just double everything?** Yes: the distance, fuel and cost all double, while the cost per 100 miles or kilometres stays the same. If the way back is a different route, work out each direction as a one-way trip. **Why might the real cost be different?** Fuel economy changes with speed, traffic, hills, weather, roof boxes and how loaded the car is, and prices vary between fuel stations. Treat the answer as a planning figure and allow a margin. **What does the cost per person include?** Only fuel, divided equally between the number of people you enter. Tolls, parking and ferries are not included, so add them separately if you share those too.