Tire Size Calculator
Calculate tire diameter, sidewall height, circumference and revolutions per mile.
Loading calculator…
What this tool does
Calculate tire diameter, sidewall height, circumference and revolutions per mile. Nominal geometric values; actual loaded rolling circumference varies with manufacturer, pressure and load.
How to use the Tire Size Calculator
- Enter or select tire width (mm).
- Enter or select tire aspect ratio (%).
- Enter or select tire rim diameter (inches).
- Read the calculated result; change any measurement to compare alternatives.
Formula
sidewall(in)=width(mm)×aspect/100/25.4; diameter=rim+2×sidewall; circumference=π×diameter; rev/mile=63360/circumference
- width
- Tire width (mm)
- aspect
- Tire aspect ratio (%)
- rim
- Tire rim diameter (inches)
Nominal geometric values; actual loaded rolling circumference varies with manufacturer, pressure and load.
Worked example
For tire size calculator, the following measurements illustrate the exact method: Tire width (mm): 225; Tire aspect ratio (%): 50; Tire rim diameter (inches): 17.
Inputs
- Tire width (mm)225
- Tire aspect ratio (%)50
- Tire rim diameter (inches)17
Result
- Tire diameter25.86 in
- Sidewall height4.43 in
- Tread width8.86 in
- Revolutions per mile779.95
Results explained
- Tire diameter
- Tire diameter from the formula above, expressed in in before metric conversion. Nominal geometric values; actual loaded rolling circumference varies with manufacturer, pressure and load.
- Sidewall height
- Sidewall height from the formula above, expressed in in before metric conversion. Nominal geometric values; actual loaded rolling circumference varies with manufacturer, pressure and load.
- Tread width
- Tread width from the formula above, expressed in in before metric conversion. Nominal geometric values; actual loaded rolling circumference varies with manufacturer, pressure and load.
- Revolutions per mile
- Revolutions per mile from the formula above. Nominal geometric values; actual loaded rolling circumference varies with manufacturer, pressure and load.
Frequently asked questions
sidewall(in)=width(mm)×aspect/100/25.4; diameter=rim+2×sidewall; circumference=π×diameter; rev/mile=63360/circumference
Use the tire sidewall markings, actual vehicle specifications or recorded fuel/price values required by the inputs. Do not mix US gallons and imperial gallons.
Nominal geometric values; actual loaded rolling circumference varies with manufacturer, pressure and load.
Yes. Change the relevant size, price or efficiency while keeping the other inputs constant. Results update immediately.
No. Check manufacturer fitment, load and speed ratings, clearance and local requirements with a qualified technician.