Why does wheel circumference matter?

Your bike computer uses wheel circumference to convert wheel rotations into distance and speed. An incorrect value means inaccurate readings.

How do I measure it myself?

Mark the tyre and ground, roll the bike forward one full wheel revolution on flat ground with rider weight on it, then measure the distance. This is the most accurate method.

Do tyre pressure and wear affect circumference?

Yes, lower pressure and worn tyres reduce circumference slightly. The effect is typically 1-3 mm, which is negligible for most purposes.

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Wheel Circumference Calculator — For Bike Computer Setup

Find the correct wheel circumference for your tyre size.

Tyre SizeSelect your tyre size — check the sidewall markings or the ISO/ETRTO code (e.g. 25-622). Note: 20-inch sizes here are ISO 406 (BMX/folding); a 451-rim wheel rolls further.

Tyre Pressure

Higher pressure = slightly larger effective circumference

Rider Weight (incl. gear)

Heavier riders compress the tyre more, reducing effective circumference

How We Calculate This

Wheel Circumference Lookup

This calculator uses the standard rolling-circumference values published in the Garmin Edge wheel-size chart and the Sheldon Brown / Crossroads cyclecomputer tables (ISO 5775 / ETRTO sizing). They are typical rolling figures averaged across manufacturers, so your exact tyre may differ by a few millimetres.

Pressure & weight adjustment

Lower tyre pressure and heavier riders compress the tyre more, slightly reducing the effective rolling circumference. The calculator applies a small, approximate correction based on your pressure and weight. This adjustment is a rough guide only, not a published figure — the authoritative method is a roll-out test.

For the most accurate result, perform a roll-out test: mark the tyre, ride in a straight line for one full revolution with rider weight on the bike, and measure the distance.

Frequently Asked Questions

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Last updated: June 2026

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.