We show that the structure constants of W-algebras can be grouped according to the lowest (bosonic) spin(s) of the algebra. The structure constants in each group are described by a unique formula, depending on a functional parameter h(c) that is characteristic for each algebra. As examples we give the structure constants C 4 33 and C 4 44 for the algebras of type W(2, 3, 4, . . .) (that include the WA n−1 -algebras) and the structure constant C 4 44 for the algebras of type W(2, 4, . . .), especially for all the algebras WD n , WB(0, n), WB n and WC n . It also includes the bosonic projection of the super-Virasoro algebra and a yet unexplained algebra of type W(2, 4, 6) found previously.