Tyre Size Calculator
Enter your wheel and tyre specs to get instant measurements — overall diameter, sidewall height, rolling radius, circumference, and more. Compare two sizes side-by-side with a to-scale visual and speedometer error analysis.
Instant Calculation
All dimensions update in real-time as you adjust width, aspect ratio, and rim size.
Speedometer Impact
See exactly how a tyre swap affects your speedo reading at 100 and 120 km/h.
Revs & Circumference
Know how many rotations per km for odometer accuracy and aftermarket speedo calibration.
Side-by-Side Comparison
Compare stock vs new tyres drawn to scale with a full dimension diff table.
Quick Presets
How it's calculated
Sidewall = 225 × (45/100)= 101.3 mm
Rim Dia. = 17 × 25.4= 431.8 mm
OD = 431.8 + (2 × 101.3)= 634.3 mm
Circumference = π × 634.3= 1993 mm
Revs/km = 1,000,000 ÷ 1993= 501.83
Cross-Section View
Full Dimensions
Overall Diameter
634.3 mm
24.97 inches
Section Width
8.86"
225 mm tyre width
Sidewall Height
101.3 mm
3.99 inches
Rim Diameter
432 mm
17 inch rim
Circumference
1993 mm
78.45 inches
Rolling Radius
317.1 mm
half of overall diameter
Revs / km
501.8
tyre rotations per kilometre
Revs / mile
807.6
tyre rotations per mile
Disclaimer: Calculations are based on nominal tyre dimensions. Actual measurements may vary by ±2–3% depending on manufacturer, load, and inflation pressure. This tool is for reference only — always consult a fitment specialist before purchasing tyres or wheels.
How to Read Tyre Markings
Section Width
The width of the tyre in millimetres, measured from sidewall to sidewall.
Aspect Ratio (%)
Sidewall height as a percentage of the section width. 45% of 225mm = 101.25mm sidewall.
Rim Diameter (inches)
The inner diameter of the tyre — must match your wheel size exactly.
Key Formulas
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