The question is does a knitter need a Niddy Noddy?
Spinners have a great use for this because they can skein their yarn to be able to wash it or set it or the next step in the process. But does a knitter need one? I think it can be handy if you take a project apart and your yarn is curly, this is the way to straighten it out.
You would wrap your yarn and wet it and let it dry while it's still on the Niddy Noddy. This is another advantage of having plastic pac pipe so it can get wet. If you have a wood one the wood may warp.
It is a brilliant invention and the simple pvc pipe version is simply genius. Easily can be constructed as a DIY project but can be purchased online for about $10.00. I'm looking at one on Etsy. Here is one I found for $15, this one is adjustable and it has a drawstring storage bag. It will depend on the size of the skein you want to make, 1 yard up to 2 yards.
For me it’s worth the money, I’m lazy and don’t want to go looking for the store to get the pvc pipes and either have them cut or cut and assemble and sew a bag. It’s worth $15 but as I say easily made at home.
If you already have one and it's not adjustable like the one I have here is the way to figure it all out. One wrap around this Niddy Noddy is approximately 56". To figure yardage for your skein, count the number of wraps around and multiply by 56". Take that number and divide by 36" and you will have your approximate yardage.