KOOVA / WHEELBUILDING
Spoke length
calculator.
Your measurements.
Both spoke lengths.
MEASUREMENT GUIDE
Your measurements,
explained.
Keep your rim specifications and hub measurements nearby. Open a guide when you need it.
Get help with your setup ↗What is ERD, and where do I find it?
Effective rim diameter describes the diameter at the intended spoke ends in the assembled rim and nipple setup. Use the rim maker's ERD specification or measure with the nipples and washers you plan to use.
A wheel-size marking such as 622 is a tyre bead-seat diameter; it does not provide your rim's ERD.
Should I enter the total number of spokes?
Yes. A 28-spoke wheel uses 28 here, with 14 spokes on each side in a conventional build. This calculator assumes an equal number on each side.
How do I measure PCD and centre-to-flange distance?
For J-Bend hubs, PCD is the diameter of the circle through the centres of the flange's spoke holes. Centre-to-flange distance is measured sideways from the hub's centre plane to each flange.
Check left and right separately. For straight-pull hubs, use the hub maker's drawing and measurement references for PCD and spoke offset.
Why do J-Bend and straight pull use different fields?
J-Bend uses the diameter of a spoke hole in the hub flange. This is a different measurement from spoke thickness.
Straight pull uses a spoke-length offset for the hub geometry. Use its specified sign and value, including zero when specified. The offset is separate from centre-to-flange distance.
The automatic straight-pull setting uses 2-cross below 27 total spokes and 3-cross from 27. Confirm that the selected pattern matches your hub before using the result.
Which wheel builds does this calculator cover?
Use it for conventional wheels with equal spoke counts on both sides. Rim asymmetry, frame offset, paired rim holes and 2:1 lacing are not modelled here.
The result is a calculated length. Available spoke sizes, nipple design and required thread engagement determine the final size to use.