Wheel Building: Spoke Length Calculation Tools & Tips

Struggling to get spoke length right for your custom wheels? We review the DT Swiss and Prowheelbuilder spoke calculators, and show you how to measure ERD accurately on ultralight carbon rims – helping you succeed on the first try.

When hand-building wheels, few things are more frustrating than miscalculating spoke length – too short and they’re unusable, too long and you have to reorder. This is especially critical when you are using LTC rims, because precision directly affects weight savings and structural integrity.
To help you build more accurately and efficiently, we have put together two spoke calculators that have been proven in countless real-world builds. They suit different hub brands. Whether you are a loyal DT Swiss user or prefer other hub brands, you’ll find the right tool here. As LTC, we want you to get it right the first time, so we have also included a practical guide on how to measure ERD on our rims.

2. Prowheelbuilder Spoke Calculator (For other hubs)

If you are using hubs from brands other than DT Swiss, we recommend the Prowheelbuilder Spoke Calculator.

Its biggest advantage is flexibility: you can search for an existing hub model or manually enter your own hub dimensions based on actual measurements.

👉 Access the Prowheelbuilder Spoke Calculator

Why rim ERD is so important – and how to measure ERD on our carbon rims

Choosing the right calculator is only the first step. Accurately measuring the rim’s ERD (Effective Rim Diameter) and hub dimensions is the key to obtaining the correct spoke length. Even a 1 mm error can result in spokes that are too long (dangerous) or too short (unusable).
At LTC, all our rims – whether 38 mm, 50 mm or 60 mm deep – have consistent design ERD values. However, if you are pairing them with specific hubs or lacing patterns, we strongly recommend that you verify the ERD yourself.