Jun 19, 2026 · Germán Guía Delgado
A free, open Freespoke alternative — length, tension & truing
Freespoke (kstoerz.com/freespoke), built by Karl Stoerzinger, is the wheelbuilder’s long-standing reference: a free spoke-length calculator backed by a big, community-fed database of hubs and rims. It’s the tool that inspired this project.
Spoke Calculator is a free, open alternative built around one idea: everything you need to calculate and build a wheel in one place — free, open, no login. Same free spirit, all in one place.
What it does
- Spoke length — exact 3D-trig math (no approximations), left and right computed independently for dished wheels, with first-class support for asymmetric rims (offset spoke bed) and straight-pull hubs that many free tools reject. The formula and intermediate values are shown, so you can check the math instead of trusting a black box.
- Multi-tensiometer tension — not just Park Tool. Convert a reading to tension on Park TM-1, DT Swiss Tensio 2, Unior, Super B, Wheel Fanatyk, Hozan and more, pick a spoke by brand/model, and balance the wheel with a live radar, per-spoke status, dish guidance, and a quarter-turn tuning plan.
- Truing simulator — a practice sandbox: turn nipples and watch how tension redistributes to the neighbours and how the rim’s dish, lateral wobble and radial hop respond. A teaching model, not build advice.
The database
Spoke Calculator ships its own hub and rim database, built from each maker’s official specifications wherever they exist and hand-validated before publishing. Every record carries its source and a confidence score; where there’s no official source yet, it’s flagged for review. It’s open: yours to use, check, and improve.
How it differs
- vs Park Tool’s app — multi-tensiometer instead of TM-1 only, plus length, dish and a simulator in one place.
- vs paid/closed calculators — free, no account, open source (MIT) with open data, and transparent math you can audit.
- vs Freespoke — Freespoke is great for spoke length; Spoke Calculator keeps that free spirit and adds multi-tensiometer tension, a truing simulator, asymmetric-rim and straight-pull support, live visualisers and an independent hand-validated database — all in one place.
Tension figures are estimates — devices drift and rims differ, so always re-measure as you build. Everything runs in your browser; nothing to install. Start with the length calculator and tell us what’s missing. New to wheelbuilding? Skim the glossary and the fundamentals guide.