Calculate your wheel circumference for accurate bike computer calibration. Select from standard tire sizes or enter custom rim and tire measurements.
Your bike computer calculates speed and distance by counting wheel rotations and multiplying by the wheel circumference. If the circumference value is wrong, every speed reading and distance measurement will be off. A 2% error in circumference means a 2% error in reported distance — that 100 km ride was actually 98 km or 102 km.
Tire size has a significant impact on circumference. Switching from a 700×25c to a 700×32c tire adds about 44mm to the circumference. Even changing brands with the same stated size can vary by 5–10mm due to manufacturing differences. For the best accuracy, calibrate whenever you change tires.
e.g., 25-622 — tire width and BSD in millimeters. The most precise and unambiguous system.
e.g., 700×25c — approximate outer diameter and width. Common for road and gravel tires.
e.g., 29×2.3" — diameter and width in inches. Common for mountain bike and kids' tires.
Select a standard tire size or enter custom rim and tire measurements to calculate circumference
| Tire Size | Diameter (mm) | Circumference (mm) | Rev / km |
|---|---|---|---|
| 700×23c (Road) | 668 | 2098 | 477 |
| 700×25c (Road) | 672 | 2111 | 474 |
| 700×28c (Road/Endurance) | 678 | 2130 | 469 |
| 700×32c (Gravel) | 686 | 2155 | 464 |
| 700×35c (Gravel) | 692 | 2174 | 460 |
| 700×40c (Gravel) | 702 | 2205 | 454 |
| 700×45c (Gravel) | 712 | 2236 | 447 |
| 29×2.1" (MTB) | 729 | 2290 | 437 |
| 29×2.3" (MTB) | 739 | 2321 | 431 |
| 27.5×2.1" (MTB) | 691 | 2170 | 461 |
| 27.5×2.3" (MTB) | 701 | 2201 | 454 |
| 27.5×2.5" (MTB) | 711 | 2232 | 448 |
| 26×2.1" (MTB) | 666 | 2091 | 478 |
| 20×1.75" (BMX/Folding) | 451 | 1416 | 706 |