Wheel Circumference Calculator
Get the circumference value to enter into your bike computer, by tire size or measured diameter.
How to use the wheel circumference calculator
- Choose a common tire size, or switch to enter a measured diameter.
- Click Calculate.
- Enter the circumference in mm into your cycling computer.
Tire size affects circumference
Two 700c tires of different widths roll out slightly differently. For best accuracy, measure your own rollout rather than relying on a chart value.
Why accurate circumference matters
Your bike computer multiplies wheel circumference by revolutions to calculate speed and distance. A wrong value makes every ride reading inaccurate, so getting it right ensures your data, segments, and pacing are trustworthy.
Measured versus chart values
Tyre charts give a good starting circumference by size, but actual circumference varies with tyre pressure, width, and load. For the most accurate computer, roll the wheel one full turn with your weight on the bike and measure the distance directly, then enter that value.
Frequently asked questions
Why does wheel circumference matter?
Bike computers count wheel revolutions, so an accurate circumference is essential for correct speed and distance readings.
How do I measure wheel circumference?
Mark the tire and floor, roll the wheel one full turn with your weight on the bike, and measure the distance between marks — that is your real-world rollout.
How do I measure wheel circumference precisely?
Sit on the bike, mark the tyre and floor at the valve, roll forward exactly one revolution, mark again, and measure between the marks in millimetres.
Does tyre pressure change circumference?
Slightly. Lower pressure and heavier loads reduce rolling circumference, which is why a measured value beats a chart figure for accuracy.
Why is my GPS distance different from my wheel sensor?
GPS and wheel sensors use different methods; a correctly calibrated wheel sensor is often more accurate for distance, especially on twisty or tree-covered routes.
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