Measure the diameter of your glasses.

Add something for two fingers.

Add something for the inebriation of the owner of the fingers.

But sometimes table space is a binding constraint, in which case there must be less paper area, hence smaller circles.

The images show the packings for the diameters ≤ 4½″ ≈ 114mm, down to slightly below 3″ ≈ 76mm.