Tyre Size Calculator
Compare tyre sizes and calculate the speedometer error when switching tyre dimensions.
Tire Size (Example: 205/55R16)
205/55R16 - Width(mm) / AspectRatio(%) Rim(inches)
Tire Dimensions
📐 Tire Measurements
🛞 Common Tire Sizes
📋 Understanding Tire Codes
205/55R16:
- • 205 = Width in millimeters
- • 55 = Aspect ratio (sidewall is 55% of width)
- • R = Radial construction
- • 16 = Rim diameter in inches
💡 Tire Selection Tips
- • Always use the size recommended in your owner's manual
- • Check sidewall of current tires for your vehicle's size
- • Larger tires may affect speedometer accuracy
- • Performance depends on tire quality and compound
- • Rotate tires every 5,000-7,000 miles
- • Replace when tread reaches 2/32 of an inch
Formula
Sidewall Height = Width × (Aspect Ratio / 100)
Diameter = (2 × Sidewall Height) + Rim Diameter
Circumference = Diameter × π
How it works
Tire Code: Width/AspectRatioRRimSize Example: 205/55R16 Sidewall Height = Width × (Aspect Ratio / 100) Tire Diameter = (2 × Sidewall Height) + Rim Diameter Circumference = Diameter × π Example (205/55R16): Sidewall = 205 × (55 / 100) = 112.75 mm Diameter = (2 × 112.75) + (16 × 25.4) = 630.7 mm = 24.82 inches Circumference = 630.7 × π = 1,981 mm = 1.98 m
The tire size calculator decodes tire markings and calculates tire dimensions. Enter your tire width, aspect ratio, and rim size to get precise measurements. Includes common tire sizes and explanation of tire codes.
Why this matters
Understanding tire sizes ensures you buy the correct replacement tires. Incorrect tire size can affect speedometer accuracy, fuel efficiency, and handling. Tire diameter changes affect gear ratios and overall vehicle performance.
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Learn more
The complete guide to tyre size calculator
Formulas, examples, and tips explained in plain English