It isn't as if kanthal is that expensive guys, and a notebook to keep notes on your
coils is nearly free as well, or keep notes in Google documents for the ultimate in penny pinching.
This way you have a very good idea of what you'll get with your own wrapping skills and equipment.
I'm almost certain very few check the kanthal for real diameter with micrometers, and I would think nobody actually checks metallurgy of their wire.
What we can check is ohms per yard/meter and extrapolate ohms per smaller unit of measure and punch a few numbers to figure out what length of wire will be needed to get a certain resistance.
The proof is of course in the final build.
Maurice.