Question

how to calculate contact lens power from spectacle power

Answer 1

by using power of lens formula.. it is 1/f

The diopter is the unit of measure for the refractive power of a lens. The power of a lens is defined as the reciprocal of its focal length in meters, or D = 1/f, where D is the power in diopters and f is the focal length in meters. Lenssurface power can be found with the index of refraction and radius of curvature.