A method for calculating a customized progressive addition surface S′″ of a progressive addition lens (PAL) made of a material having an optical index of n, the method, comprising at least the successive steps of: a) providing N initial progressive addition surfaces where N≧1, b) calculating N intermediate surfaces S′k by flattening each initial progressive addition surfaces Sk, c) calculating a transformed intermediate surface S″, d) calculating the customized progressive addition surface S′″ by cambering the transformed intermediate surface S″.