Ive been asked to make some beads for a semi local artist and was wondering if anybody had a formula to figure out the starting size of a disc for various sized beads, ie diameter of a disc to make a 1/2 inch diameter bead out of 22, 20 , or 18 ga sheet, we haven’t decided on a thunk was yet. I know that with alittle time I could figure it out the long way but I don’t want to waste the materials and I’m not great with math. I can follow a formula but coming up with one is out of my league, thanks in advance 

take a 1 inch disk.  make the bead, measure it and there is your formula, if its a 1/2 inch bead you know its a 2 to 1 ratio

 

Thanks Steve 

Surface area---half of a sphere would get you close; then it depends on how much thinning you do working it to shape.

Surface area of 1/2 sphere;

A=4pi(r sq.)/2. Sorry I don't have symbols

Alternatively; A=C×r,  C is circumference and r is radius of the sphere. The area of a sphere is equal to the lateral area of a cylinder circumscribed around it.

So A=C×D

Theoretically a disc with the same area as the intended 1/2 sphere would work, but that doesn't take into account stretching and forming