The spiritual successor to Freespoke

The free, open bicycle-wheel spoke calculator.

Exact spoke lengths, multi-tensiometer tension, and a live truing simulator — with an open hub/rim database and transparent math. No login, no paywall.

Open the calculator → Tension a wheel

Spoke length Exact 3D-trig math, left & right independent, asymmetric-rim & straight-pull aware, open hub/rim DB. → Tension Multi-tensiometer — not just Park Tool. Per-spoke status, balance radar, dish & quarter-turn tuning plan. → Truing simulator Practice sandbox: turn nipples and watch tension, dish, lateral wobble & radial hop respond. →

Why this one

✓ Multi-tensiometer (Park, DT Swiss, Unior, Super B, Hozan…)
✓ Asymmetric rims (offset spoke bed) & straight-pull hubs
✓ Transparent math — formula and intermediate values shown
✓ Open hub & rim database, hand-validated against maker specs
✓ Free, no login, runs in your browser

From the blog

All articles →

Jun 21, 2026 Wheelbuilding fundamentals: spoke length, tensioning order, and de-stressing Three things that decide whether a wheel stays true: getting spoke length right before you build, tensioning in the right order (leading vs trailing, the Markling Method), and de-stressing. A practical guide tied to the calculator.
Jun 20, 2026 How to measure ERD — the #1 spoke-length error ERD (Effective Rim Diameter) is where most spoke-length calculations go wrong. Here are the two measurement conventions, a worked example, and why ERD dominates your accuracy.