Thanks for the advice.. I'm making my spools out of PVC and old cd's at the moment.

What I'm really hoping to do is to have as little waste as possible. The expense of the wire wasn't a small one and I'd hate to have lengths too short to wind other coils with. I have other projects I want to do as well after I wind this coil.

I'm sure over time I'll be getting more wire, especially if I want to scale up or down for different projects.

From what I've read, there are between 100 and 250 feet worth of wire for 450 turns. What I'd like is to have an exact way to calculate the length (with the consideration of the final twisted strand) at 450 turns. Maybe I can get close without going over and save what little wire I was able to afford. I'm sure there are a lot of considerations for this kind of calculation though.