Right this is complete unknown territory to me so I am looking for some advice. I am getting some new wheels built and currently ordering in the parts.

The hubs will be Pro 4 boost and rims WTB whic have an ERD or 564mm.

Can anyone point me in the right direction on how I calculate what spoke length I need?

Who’s building them for you? If they can build a wheel I’m sure they could advise spoke length.

Having said that, Try these for size –

https://www.wheelpro.co.uk/spokecalc/
https://spokes-calculator.dtswiss.com/en/

Don’t necessarily believe the published ERD either – much better to measure the parts yourself once you physically have them

If your not building them I’d probably leave the spokes to the builder to supply as it will save you getting left with stuff if you order the wrong length.

The online calcs are good but do not always get things right if your useing publishes figures rather than measured ones

Thanks. I haven’t spoke to a wheel builder yet, I was planning on taking it to my LBS and leaving the parts with them but as you say it maybe easier to let them order in. I was just trying to save some time.

With hope stuff you may find your lbs is competitive on price with the mail order sharks.

Have you asked for any quotes for fully built wheels and for build only costs ?

Your builder may very well not appreciate being given spokes to work with rather than being left to calculate for themselves. If they build wheels regularly enough to be worth allowing to do the job they almost certainly have spokes in already anyway, and usually parts used for wheel build are priced below the usual over-the-counter price. As Jimmyoto says, it’s a bad idea trusting online numbers for sizes of things rather than measuring what came out of the box. Perfectly acceptable manufacturing tolerances can make nonsense of the published numbers.

If you do end up ordering spokes I always get mine from rose bikes. Even with high postage they still work out
Cheaper.

I wouldn’t order them based on quoted dimensions for parts though, I always measure them since many manufacture measure erd differently, and there is often loads of versions of hubs although hope ones might not be two bad. I always use the wheel pro site for calculating lengths. It has recently changed though so you take the length it says and round up.

I use JE James for Sapim spokes. Reasonably priced and available individually.

JustRidingAlong are good for Sapim spokes too – stock a wide range of sizes. Buy one of their 100 bags of nipples not just the number you need.