About

I'm Ger, and I've been mad about bikes for years. I'm a developer by trade, curious and largely self-taught, so I love being self-sufficient with everything my hobbies involve. Over the years, through trial and error, I've kept learning and cementing what I know. Spoke Calculator is the tool I wish I'd had when I started building wheels. Back then I had a handful of separate tools I reached for depending on the job. This calculator is my attempt to pull all those scattered tools into one place, plus new features I'd missed when I started and decided to build.

Where this started

My wheelbuilding started on a forum. Years ago on foromtb, deep in a thread called «ruedas endureras a la carta. EL POST» (custom enduro wheels, built to order), I read enough people lacing their own that I stopped outsourcing it and bought my first set of spokes and tools. The first wheel was hard: there were a lot of concepts I didn't know and the process was slow. With that first one done, and the satisfaction of having built it from scratch, the second followed. I've hand-built fourteen-plus wheelsets since: folders, enduro, gravel, fatbikes, rigid steel, kids' bikes. And I still get the same quiet satisfaction every time I finish adjusting the tension and the wheel runs true.

Ger riding an enduro bike into a rocky descent at a viewpoint, above a sea of clouds — Above the sea of clouds, on wheels built at home.

The tool almost everyone leaned on was Freespoke (kstoerz.com/freespoke), Karl Stoerzinger's free spoke calculator with its huge community-fed database. It was my reference, and it's what helped me get into lacing wheels.

What this is

I built Spoke Calculator because I wanted to bring together what you need to calculate and build a wheel without hopping from page to page: spoke-length calculations, multi-tensiometer tension, a truing simulator, and an open hub and rim database with source information. The same free spirit as Freespoke. Here you can calculate lengths with asymmetric rims and manufacturer-specified straight-pull offsets. The visualisers show layouts the tool can model, not every possible wheel build.

Data

Hubs & rims: the database includes manufacturer specifications and historical records awaiting review. Check each part's provenance and notes: an official source does not certify that I have measured or hand-validated it.
Tension: some tables come from manufacturers, others from third-party compilations. The tool shows each table's source and version; not all are official.

How the numbers are made

Spoke length comes from a 3D geometric model, and the formula and intermediate values are shown so you can check the numbers yourself. The result depends on the measurements and model assumptions: it does not guarantee a buildable wheel. Tension is estimated from a table for the selected tensiometer and spoke profile, without extrapolating beyond its range. Calibration and table choice matter, so re-measure as you build and follow the manufacturer's limits.

The technical documentation contains length and tension reference checks with reproducible inputs and outputs, table sources and the scope of the software tests.

Get involved

Build wheels and spot a number that looks wrong? Missing a hub, rim or tensiometer? Tell me. Corrections to the data matter most: accuracy is the whole point, and I'd rather you catch my mistake than the next builder inherit it.