What this site is
CarRunningCosts is a small set of free calculators for UK drivers: fuel cost for a specific journey, true cost per mile including insurance and servicing, a fair way to split fuel between passengers, and a straightforward EV-versus-petrol running cost comparison. There's no sign-up, no app to install, and no data saved between visits — you enter your numbers, get an answer, and that's it.
Why we built it
Most fuel calculators found online are either built around US units (the wrong size of gallon, for a UK audience), buried in irrelevant content, or too simplistic to give a genuinely useful number for anything beyond a single tank of fuel. This site tries to do a small number of things properly: correct UK units throughout, calculations that are shown plainly rather than hidden behind a "black box", and enough surrounding context to actually use the number sensibly.
How the calculations work
All fuel-based calculators convert your inputs to miles and UK miles per gallon if needed, then use the correct UK imperial gallon (4.54609 litres) to work out fuel used and its cost. The Cost Per Mile Calculator adds your annual insurance, servicing and other running costs on top of fuel to give a genuinely complete per-mile figure. The EV vs Petrol Calculator runs the same annual mileage through both a petrol-cost calculation and an electricity-cost calculation based on your miles-per-kWh figure, so the comparison is like-for-like.
What it doesn't cover
These tools don't account for vehicle depreciation, finance or lease payments, one-off repair costs, or the purchase price difference between different types of car — they're deliberately focused on the running costs you pay as you go. If you need a full cost-of-ownership figure, treat the numbers here as one input into that larger picture rather than the whole answer.
Have a question, spot an error, or want to suggest another calculator? Get in touch.