Tire & Wheel
Tire Size Calculator
Overall diameter, circumference and sidewall height from a tyre size code like 225/45R17.
diameter = rim × 25.4 + 2 × (width × aspe…
Also called tyre size calculator · tire diameter calculator
Auto & Travel · 4 calculators
Tire & Wheel Calculators
Tire size, diameter and circumference, tire comparisons, speedometer error, wheel offset and backspacing.
Tire & Wheel
Tire Size Comparison Calculator
Compare two tyre sizes for diameter, width and speedometer effect before changing wheels.
difference % = (new diameter − old diamet…
Also called tire size difference · plus sizing calculator
Tire & Wheel
Speedometer Error Calculator
How a tyre size change shifts your speedometer and odometer readings.
actual speed = indicated × new diameter ÷…
Also called speedo error calculator · odometer error
Tire & Wheel
Wheel Offset Calculator
How changing wheel offset and width moves the wheel in or out of the arch.
outer edge = width ÷ 2 − offset
Also called et offset calculator · wheel spacer calculator
Key tire & wheel formulas
| Tire Size | diameter = rim × 25.4 + 2 × (width × aspect ÷ 100) |
|---|---|
| Tire Size Comparison | difference % = (new diameter − old diameter) ÷ old diameter × 100 |
| Speedometer Error | actual speed = indicated × new diameter ÷ old diameter |
| Wheel Offset | outer edge = width ÷ 2 − offset · inner edge = width ÷ 2 + offset |
Tire & Wheel questions
What does 225/45R17 mean?
225 mm wide, sidewall 45% of that width (101 mm), radial construction, fitting a 17 inch rim.