Spoke Length Calculator
Free spoke calculator for wheel building. Enter hub flange dimensions and rim ERD, or choose from common hub presets to get drive-side and non-drive-side spoke lengths instantly - accurate to ±0.1 mm.
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Why Accurate Spoke Length Matters
Getting the right spoke length is the foundation of a well-built wheel. Spokes that are too long risk protruding through the nipple and puncturing the rim tape or inner tube, while spokes that are too short won't have enough thread engagement in the nipple, leading to a weak and unreliable wheel.
Professional wheel builders aim for spoke lengths accurate to within ±1 mm. Our calculator uses the standard geometric spoke length formula that accounts for hub flange radius, center-to-flange distance, rim ERD, spoke count, and cross pattern - the same method used by experienced mechanics worldwide.
Understanding the Key Measurements
Hub Flange Diameter
The diameter of the bolt circle of spoke holes on the hub flange. Measure center-to-center across opposite spoke holes using calipers. Larger flanges generally result in stiffer, shorter-spoked wheels.
Center-to-Flange
The distance from the hub centerline (midpoint between locknuts) to the center of each flange. On rear hubs this is asymmetric - the drive side is closer to center due to the cassette body.
Effective Rim Diameter (ERD)
The diameter of the circle where the spoke ends sit inside the rim. This is not the same as rim size (e.g., 700c). Check your rim manufacturer's specs or measure it directly using two opposing spokes and nipples.
Cross Pattern
How many times each spoke crosses other spokes from hub to rim. 3-cross is the most common for road and MTB wheels, providing excellent durability and power transfer. Radial lacing is sometimes used on front non-disc wheels.
Spoke Length Tips for Wheel Building
- Always round downwhen ordering spokes. A spoke 0.5–1 mm short is far better than one that's too long.
- Verify your ERD - manufacturer specs occasionally differ from actual measurements. When in doubt, measure it yourself.
- Rear wheels need two lengths - the drive side is almost always shorter than the non-drive side due to hub dish.
- Front disc hubs are also asymmetric (rotor side vs. non-rotor side), so calculate both sides separately.
- Buy a few extras - order 2–4 spare spokes of each length for future repairs.
Common Rim ERD Reference
Below are typical ERD values for popular rim types. Always verify with the manufacturer's spec sheet before building.
| Rim Type | Wheel Size | Typical ERD (mm) |
|---|---|---|
| Road clincher (low profile) | 700c | 600–606 |
| Road clincher (mid-depth 30–40 mm) | 700c | 580–596 |
| Road deep-section (50+ mm) | 700c | 556–578 |
| MTB 29er (standard) | 29" / 622 | 596–604 |
| MTB 27.5" | 27.5" / 584 | 560–568 |
| Gravel / CX | 700c | 596–606 |
Common Hub Flange Dimensions
Reference flange measurements for popular hubs. Measure your own hub with calipers to confirm - manufacturing tolerances vary.
| Hub | Type | Flange ⌀ (mm) | Left C-to-F | Right C-to-F |
|---|---|---|---|---|
| Shimano 105 R7000 | Front | 45 | 33.0 | 33.0 |
| Shimano 105 R7000 | Rear | 45 | 35.0 | 17.5 |
| DT Swiss 350 | Front | 56 | 27.0 | 27.0 |
| DT Swiss 350 | Rear | 56 | 33.6 | 17.4 |
| Industry Nine Hydra | Front | 58 | 26.2 | 26.2 |
| Chris King R45 | Rear | 57 | 33.0 | 17.0 |
Frequently Asked Questions
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