Tools

Convert a sphero-cylindrical prescription between plus-cylinder and minus-cylinder form. Enter sphere, cylinder and axis and the calculator returns the transposed Rx instantly, with the shared spherical equivalent.

Enter your prescription below to compare lens thickness and weight across seven refractive indices, from standard CR-39 to 1.74 ultra-thin. The calculator uses the sagitta formula and ANSI Z80.1-2025 minimum thicknesses to estimate edge thickness (minus lenses) or center thickness (plus lenses) for each material, so you can see exactly how much thinner and lighter each upgrade gets.