Bracelet sizing

[Polly]

I believe the amount you need to add for larger beads would be the average size of the beads you're using, times pi (3.14).
So if using 16mm beads, 16mm x 3.14 = 50.24mm, or about 2".
Does that sound like the right amount that you've run into?  We tested the equation, coming at it from 3 different ways, but have not actually strung a bracelet using it.
(The person I had test my equation has a minor in math and in physics, and he came it a **completely** different way than I did, but ended up with the same results.)
--Polly

[Divine Creations]

Help!  How do I determine the size of a bracelet when using large stones.  I generally make my bracelets 7 1/2" long, but find that when I use large stones (8-16MM) the bracelet becomes too small.  I have heard that there is a formula for determining the size of a bracelet while taking the bead or stone size into consideration.  Does anybody know this?  Thank you