Tire size calculator
Decode tire dimensions such as 205/55R16.
Formula
Sidewall = width × ratio/100; diameter = rim + 2×sidewall; circumference = π×diameter
Section width: 205 mm · Rim diameter: 16 in · Sidewall height ≈ (205 mm × 0.001 m/mm)×(55)×10 · Nominal diameter ≈ (16 in × 0.0254 m/in)×1000+2×(112.75) · Diameter in inches ≈ (631.9)÷25.4 · Nominal circumference ≈ (631.9)×pi÷1000
How to use
- Enter section width, usually in millimeters.
- Enter aspect ratio and rim diameter.
- Read the nominal unloaded dimensions.
Examples
- 205/55R16 gives 112.75 mm sidewall and 631.9 mm diameter.
Frequently asked questions
What does 55 mean in 205/55R16?
Sidewall height is 55% of the nominal 205 mm section width.
Is this measured rolling circumference?
No. Load, inflation, wear and manufacturer design affect real dimensions.
Does this approve a replacement tire?
No. Check vehicle-approved sizes, load and speed ratings and clearance.
Sources
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