Speedo Formula

All,
I know there is some information out there for which speedo goes with
which rear-end gear, but has anyone made a spread sheet with formulas
that lets you plug in tire diameter(maybe from a chart) and rear-end
gear ratio and gives which speedo gives the closest reading and how much
it is off by?
Dean Swanson
Holly Springs, N.C.
'62 A.H. Sprite mkII