How to Calculate Spoke Length for Your Wheel Build

September 4, 2026

What You Need Before You Start

To calculate spoke length accurately, you'll need four measurements:

Effective Rim Diameter (ERD) — the internal diameter of the rim at the point where the nipple seats
Hub flange diameter — measured centre-to-centre of the spoke holes on each flange
Hub centre-to-flange distance — from the centre of the hub to each flange (left and right separately)
Number of spokes and lacing pattern — e.g. 32h, 3-cross

Most rim manufacturers publish ERD in their specs. If not, measure it yourself using two spokes and nipples inserted opposite each other.

I recommend using Vernier calipers and a good quality spoke ruler for hub measurements, accuracy is important here.

The Spoke Length Formula

The standard formula for spoke length is:

L = √( R² + F² + D² − 2RF·cos(θ) ) − d

Where:

L = spoke length (mm)
R = ERD ÷ 2
F = hub flange radius (flange diameter ÷ 2)
D = hub centre-to-flange distance (for the side you're calculating)
θ = crossing angle = (360° ÷ number of spokes) × number of crosses × 2
d = spoke hole diameter on the flange (typically 2.5mm) ÷ 2

In practice, most builders use a spoke length calculator. I tend to use spoke length project which is subscription based, free ones can be found at Spoke Calc or Edd by DT Swiss and input these values directly. The formula above is what those tools run under the hood.

A Practical Example

Building a 32h rear wheel, 3-cross, with a standard road hub and a 700c rim with an ERD of 598mm:

R = 299mm
F = 46mm (flange diameter 92mm)
D (drive side) = 17mm, D (non-drive side) = 34mm
θ = (360 ÷ 32) × 3 × 2 = 67.5°

Plugging these into a calculator typically gives something like 296mm drive side / 298mm non-drive side — always round to the nearest whole millimetre and check against the manufacturer's available lengths.

Choosing the Right Spoke

Once you have your length, the next decision is spoke type. For most road and gravel builds:

DT Swiss Champion 14g Black — a reliable, round-section stainless steel spoke ideal for everyday builds and training wheels. Also available in silver.
Sapim Race 14g Black 270–310mm — a double-butted spoke that saves weight while maintaining strength, well-suited to performance road and sportive builds. Also in silver.
Sapim D-Light 14g Black 256–300mm — a lighter double-butted option for weight-conscious builds where spoke count is lower. Also in silver.

For track and fixie builds, a round-section spoke like the DT Swiss Champion handles the fixed drivetrain stresses well.

Tips for a Successful Build

Always calculate drive and non-drive sides separately on rear wheels — the asymmetry matters
Add 1–2mm if you're unsure; it's easier to trim thread engagement than to deal with a spoke that's too short
Use spoke prep or thread lock on nipple threads to prevent loosening under load
Tension evenly and stress-relieve the spokes before final true