Tire Size Calculator

Thinking of upsizing or swapping tires? Enter two sizes in P-metric format (width/aspect-ratio/rim) and compare diameter, circumference, clearance and how much your speedometer will be off.

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🔃 Instant math

Diameter, sidewall and circumference computed from the P-metric numbers.

📠 Speedo check

See exactly how fast your speedometer reads wrong after the swap.

🚘 Plus sizing guide

Keep diameter within ~3% to avoid rubbing and ABS issues.

🔒 Private

All local β€” nothing is uploaded.

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Wheels, ratios and speed.