Bicycle Spoke Length Calculator
Enter your rim ERD, hub flange diameter, center to flange distance, spoke count and cross pattern to get the spoke length in millimetres.
How to calculate spoke length
- Enter the rim effective rim diameter (ERD) in millimetres.
- Enter the hub flange diameter and center to flange distance.
- Set the spoke count and cross pattern, then read spoke length.
Examples
32 spoke, 3 cross build
ERD 600, flange 44, center to flange 35, 32 spokes, 3 cross
about 293.08 mm
Radial (0 cross) build
ERD 600, flange 44, center to flange 35, 32 spokes, 0 cross
about 278.89 mm
Frequently asked questions
What is ERD in wheelbuilding?
ERD is the effective rim diameter, the diameter across the points where spoke ends seat. It is the single most important rim number for spoke length.
What does cross pattern mean?
Cross count is how many other spokes each spoke crosses on its way from hub to rim. Common road builds use 3 cross, while 0 cross is a radial lacing.
How is spoke length calculated?
It uses the law of cosines on the rim radius, flange radius, center to flange offset and the lacing angle, then subtracts half the spoke hole diameter.
Why measure each side of the hub?
Front and rear hubs are usually asymmetric, so the left and right flanges sit at different offsets. Calculate each side separately for an accurate build.
What spoke hole diameter should I use?
Most hub flanges use a 2.6 mm spoke hole, the default here. Adjust it if your hub specification lists a different flange hole diameter.
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