19 Jun 2026 · updated 15 Sept 2026 · Ger

A free, open Freespoke alternative: spoke length and tension

Freespoke, built by Karl Stoerzinger, inspired this project. Spoke Calculator is an independent, free alternative with a length calculator, tension conversion and a truing simulator on the same site. You don’t need an account to use them.

If you are coming from Freespoke, start with the same hub and rim measurements. Check the ERD reference and offset direction when copying them across. You can then use the result to prepare a tension record for that wheel.

If you need to choose spoke lengths

Open the length calculator and select catalogue parts or enter their measurements manually. Each side has a raw result and a rounded commercial length. Open the formula to see how the result was calculated.

Measure ERD with the nipples and washers you intend to use. The ERD guide shows my 542 mm measurement with the spoke tips flush with the tops of the nipple heads. It also explains how that differs from Park Tool’s bottom-of-slot reference. Record which reference you chose.

For an asymmetric rim, enter the offset distance without a minus sign and select the side the holes sit towards, viewed from the rider’s position. A straight-pull hub requires the manufacturer’s spoke offset for each side. That value is used for length; follow the hub’s pattern when lacing. The drawing covers conventional J-bend layouts with equal spoke counts on each side. It excludes 2:1, G3 and paired-hole layouts.

Check both raw lengths, rounding and nipple thread engagement before ordering. If you are comparing calculators, use exactly the same measurements and reference points to trace any difference.

If you are already measuring tension

In the tension tool, select the instrument and exact spoke profile, then enter your readings. Each side’s summary shows its mean and the differences between spokes. Balance / Target selects the radar reference; working windows show the limits in both kgf and instrument readings.

You can import another conversion table through My tension tables. Check the instrument, spoke, units and source before using it. Custom tables support measurement and comparison, with turn advice and simulator loading disabled.

Check meter calibration and set the target and tolerance according to the rim maker’s guidance. The entire band must fit within the permitted maximum. A reading outside the table is flagged so you can check the profile or repeat the measurement.

If you want to practise truing

The simulator lets you explore which part of the wheel moves when you tighten or loosen nipples. Practise adjustment direction and watch the changes in radial true and dish. Its response is qualitative: on the real wheel, make a small correction and measure again to see how much has changed.

Save your work and carry on another day

Name the build and save it in your browser. Length and tension have their own records; export both JSON files to keep the geometry and readings. You can also copy their links to open them in another browser. A tension record using a custom table includes the exact revision used.

Tension this wheel carries the name, wheel identity and geometric tension split from length into tension setup. Check the targets before measuring: the initial 110 kgf is a provisional value to adjust for your build.

The hub and rim catalogues show where their measurements came from. They include manufacturer documents, historical records and entries awaiting a source. Open the part’s notes and check uncertain dimensions against the actual component. For the whole process, follow the wheelbuilding guide.