Approximate formulae of wave-current friction coefficient and phase difference, spanning all flow regimes, are obtained. Both of them are based upon the theoretical results of Tanaka and Shuto (1981). No restriction is made regarding the intersection angle between waves and current. Since all the formulae are given in an explicit form, they can reduce computing time when they are applied to practical problems. Comparisons are made not only with the exact solutions but also with experimental data. The accuracy of these formulae is found to be satisfactory.