CalculatorsWheel Circumference Calculator

Wheel Circumference Calculator

GPS computers still want a wheel circumference when you use a speed sensor. The figure is the full circle of the loaded tyre, approximated here from bead seat plus two labelled widths.

Inputs

Bead seat diameter (mm)622 for 700c/29, 584 for 650b, 559 for 26.Tire width (mm)

Results

Circumference: 84 in

How the number is made

Circumference mm = π × (bead-seat diameter + 2 × tyre width). 700c and 29-inch share 622 mm. 650b is 584. A traditional 26-inch is 559.

A roll-out test on the garage floor (valve at the bottom, one revolution, measure) beats this estimate for a final sensor calibration.

Related calculators

Cadence to Speed Calculator
Uses this circumference to turn a gear into km/h.
Tire Pressure Calculator
A soft tyre shortens the real circumference slightly.

Questions

Why not the number printed on the tyre?

700×28c is a label. The computer wants millimetres of circumference, which changes with width, pressure and rim.

How do I measure it for real?

Sit on the bike, valve at the bottom, roll one revolution, mark the floor, measure. Use this calculator when you cannot do that yet.

Is this the millimetre figure a GPS unit wants?

It is the circumference of the labelled diameter: bead seat plus twice the tyre width. A soft tyre rolls a little shorter than that figure.

Related gear

Speed sensor
Enter this millimetre value if the computer asks for wheel size instead of a tyre label.
$30–$60

Disclaimer — no professional advice, no liability

These calculators are simplified estimates for education. They are not a bike fit, a structural inspection, or a torque specification that overrides the number printed on a part. Confirm chain length, spoke length, tire fit and bolt torque on the bicycle before you ride.

These calculators, pages and any related content are provided “as is” and “as available”, solely for general educational and informational purposes. They are simplified mathematical estimates, not a professional bike fit, a structural inspection, a manufacturer torque specification or a training, nutrition or medical plan.

Results can be wrong, incomplete or inapplicable to your frame, wheels, tires, drivetrain or suspension. You must independently verify every figure, assume all risk, and confirm chain length before you cut, spoke length before you lace, tire and rim compatibility before you inflate, and the torque printed on the part before you tighten it.

To the fullest extent permitted by applicable law, the site operator, authors, contributors and affiliates disclaim all warranties, express or implied, and accept no liability for any direct, indirect, incidental, special, consequential or punitive damages, or for property damage, injury, death, business interruption or financial loss, arising out of or related to the use of, or reliance on, these tools or their outputs.

Some jurisdictions do not allow certain warranty exclusions or liability limitations, including for personal injury. In those places, our responsibility is limited to the maximum extent permitted by law. If you do not agree, do not use this site.