Lens maker formula is the formula for the manufacturer of lenses. Given the specification of the lenses in terms of power (long distance and short distance), they make the lense using the proper combination of glass, with appropriate radii of curvature.
1/f = (μ-1) [1/R1 - 1/R2]
this is the formula, f = focal length, 1/f = power of lens, R1 and R2 are radii of curvature. μ = refractive index of glass used. R1, R2 and f are quantities, positive in the direction of light rays.