What is this calculator?
Calculate tyre diameter and circumference from the size markings.
What can you use it for?
Use it for practical planning, conversions, measurement or checking the result described here. Calculate tyre diameter and circumference from the size markings.
How to use it
- Enter section width (mm).
- Enter aspect ratio (%).
- Enter rim diameter (in).
- Select Calculate (or Generate for random tools).
- Read the answer and any additional results below the form. Check the units and the limits of the method.
Formula and method
Circumference = pi × (rim diameter × 25.4+2 × section width × aspect ratio/100)
The formula uses the units and definitions shown above. Each input is substituted before the arithmetic is evaluated; the calculated output is rounded for display.
Worked example
Section width (mm): 205, Aspect ratio (%): 55, Rim diameter (in): 16. The result is 631.9 mm (overall diameter).
Assumptions and limits
Use the units and formats shown in the input labels. Actual conditions and applicable standards may differ from this simplified calculation.
Frequently asked questions
What inputs does the Tire Size Calculator need?
Use section width (mm), aspect ratio (%), rim diameter (in). Read the answer and any additional results below the form. Check the units and the limits of the method.
What assumptions apply to the Tire Size Calculator?
Use the units and formats shown in the input labels. Actual conditions and applicable standards may differ from this simplified calculation.