Tire, wheel and fuel calculators
Fast, accurate tools for drivers: compare tire sizes, check speedometer error and wheel offset, and work out MPG and fuel costs. Every formula is explained, and US, UK and metric units are supported.
Tire & wheel calculators
- Tire Size CalculatorDiameter, width, sidewall and revs per mile from any tire size.
- Tire Size Comparison & Speedometer ErrorCompare two sizes side by side and see the real speed at each speedometer reading.
- Metric to Inch Tire Size ConverterConvert 265/70R17 to inches and 33x12.50R15 to metric.
- Wheel Offset CalculatorHow far new wheels move in and out, with backspacing.
- Plus Size Tire CalculatorAlternative sizes on bigger or smaller rims within ±3 % diameter.
- Tire Size & Gear Ratio RPM CalculatorEngine RPM before and after a tire change, and the axle ratio to fix it.
Fuel calculators
- Trip Fuel Cost CalculatorWhat a drive will cost in fuel, return trip and split between passengers.
- MPG CalculatorYour real fuel economy from miles and gallons (or km and litres).
- Fuel Economy ConverterMPG (US), MPG (UK), L/100 km and km/L.
- Fuel Cost ComparisonYearly fuel cost of two cars and how long savings take to add up.
- Tire Size & Fuel Economy CalculatorCorrect your MPG and odometer after fitting different size tires.
Popular tire sizes
Vehicle data from official sources
- Tire & wheel sizes by vehicleFactory sizes, rims and offsets for 938 models, from Swiss government type approvals.
- US fuel economy by modelEPA city, highway and combined MPG — 5,170 model-year pages.
- UK fuel economy by modelOfficial VCA mpg, CO₂ and EV range for 869 models, NEDC and WLTP kept apart.
Why trust these calculators?
Each calculation uses exact unit definitions (1 inch = 25.4 mm, 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L, 1 UK gallon = 4.54609 L) and is checked against reference values in automated tests. Vehicle data comes only from official open-data downloads, with the source named on every page. Results are a guide: always confirm sizes with your vehicle's placard or a tire professional.