TIRE & WHEEL LAB
Tire Size Calculator
Turn the numbers on your sidewall into dimensions you can actually use.
Your results
LIVE CALCULATIONResults will appear here when JavaScript loads. See the worked example below for a reference calculation.
How this calculator works
Sidewall in mm = width × aspect ratio ÷ 100. Rim diameter in mm = rim inches × 25.4. Revolutions per km = 1,000,000 ÷ circumference in mm.
Read the full methodology for definitions, conversion factors and limitations.
Worked example
205/55 R16 has a 112.75 mm sidewall and a 631.9 mm overall diameter. Its nominal circumference is about 1,985.2 mm.
Before you act on the result
Tire and wheel dimensions cannot confirm fitment. Check wheel width, offset, suspension and wheel arch clearance, load and speed ratings, and manufacturer recommendations. Ask a qualified tire professional to verify modifications. Actual tire measurements vary with construction, pressure, load and wear.
Frequently asked questions
What does the R mean?
R describes radial construction. It is not a radius measurement. The number after R is the wheel diameter in inches.
Can I enter flotation sizes?
This calculator accepts metric passenger-style sizes such as 205/55 R16. Flotation formats such as 33×12.50 R15 are not supported.