Calculate a wheel and build it
The free, open bicycle-wheel spoke calculator.
Work out exact spoke lengths, convert any tensiometer reading, and practise truing in a live simulator. The hub and rim database is open and the math is shown, not hidden. No login, no paywall.
Why this calculator?
- ✓ Reads more than Park Tool: DT Swiss, Unior, Super B, Hozan and others.
- ✓ Handles asymmetric rims (offset spoke bed) and straight-pull hubs.
- ✓ Shows the formula and the intermediate values, so it is not a black box.
- ✓ Open hub and rim database, hand-validated against maker specs.
- ✓ Free, no login, and it runs in your browser.
From the blog
All articles →- Jul 3, 2026 Build a wheel from start to finish with Spoke Calculator The full workflow: measure hub and rim, calculate both spoke lengths, order, lace, tension with any tensiometer, de-stress and save the build. One guide, every tool.
- Jun 20, 2026 How to measure ERD: the #1 spoke-length error ERD (Effective Rim Diameter) is where most spoke-length calculations go wrong: the two conventions, a worked example, and why it dominates accuracy.