Tyre Size Comparison Calculator
Compare two tyre sizes side by side: diameter difference and how much your speedometer will be off.
Enter your values and press Calculate.
How to use the Tyre Size Comparison calculator
Most tyre fitters recommend staying within ±3% of the original diameter.
Formula
Actual speed = indicated speed × new diameter ÷ old diameter
More automotive calculators
Fuel Economy (MPG) CalculatorYour car’s real MPG and cost per mile.Journey Fuel Cost CalculatorFuel cost for a journey or road trip.Fuel Economy ConverterConvert MPG, UK MPG, L/100 km and km/L.EV Charging Cost CalculatorCost to charge an electric car.EV Charging Time CalculatorHow long an electric car takes to charge.Tyre Size CalculatorTyre diameter, width and revolutions from a size code.Horsepower CalculatorHorsepower from torque and RPM.Engine Displacement CalculatorDisplacement from bore, stroke and cylinders.Compression Ratio CalculatorStatic compression ratio of an engine.Gear Ratio & Speed CalculatorVehicle speed from RPM, gearing and tyre size.Carburetor CFM CalculatorCarburetor size for an engine.Speedometer Error CalculatorTrue speed after changing tyre size.