Works with any mix of units — distance, efficiency and price don't need to match.
Enter one value and see it converted to every other fuel-economy unit at once.
Enter a tire code in the standard format, e.g. 225/45R17
Two independent estimation methods — both give rough, ballpark figures, not dyno-verified numbers.
L/100 km = 235.214583 ÷ mpg(US), and UK gallons are 4.54609 L vs 3.78541 L US. Trip cost is distance ÷ economy × fuel price after all three are converted to matching units. You enter the economy and price — nothing is looked up from a vehicle database.
A UK (imperial) gallon is 4.54609 litres, while a US gallon is 3.78541 litres — the same real-world fuel economy converts to a different mpg number depending which gallon is meant, so the calculator converts between them explicitly rather than treating "mpg" as one universal unit.
You supply the fuel economy figure — from your car's trip computer, a fill-up calculation, or the manufacturer's rating. The calculator converts and applies that number; it doesn't look anything up from a vehicle database.
They're related but separate calculations grouped on the same page because a driver working out fuel economy often needs them together — tire size affects your true rolling speed versus your speedometer reading, and gearing/RPM affects real-world efficiency.
Distance divided by fuel economy, multiplied by fuel price, after converting all three values to matching units first — so mixing a UK mpg figure with a US-gallon fuel price, for example, still gives the correct cost.