Spoke Size / Spoke Length Database - What size spokes do I need?

I always tend to round down and usually take another mm off. Better to reach the recommended spoke tension and risk having a few threads showing rather than reach the end of the thread with the spoke still loose.

It's a controversial subject. Not engaging enough threads in the nipple can cause problems. Being 1mm too long definitely won't.

Spoc calc gave me 290,3 to 291,3 for my current build (varies very slightly for disc brake sides, and short trials freehub side). I could only get even number spoke lenghs, so figured I'd round down to 290 (I tend to agree with arup, sorry BMMF).

Thing is, DT Swiss spoc calc assumed 12mm long nipples and I have 13mm ones. I'm curious to wether...

13mm nipple + 290 spoke = 12mm nipple + 291 spoke.

I'm sure its too little to matter. I just like to get things spot-on :)