The Bertz formula for calculating molecular complexity is a sum of bond connectivities. This is converted to a simpler form based on the number of hydrogens attached to each atom. Also, the calculation of symmetry terms is derived from simple equations applied to atoms of the same equivalence class. We outline here a simple program (CPXCAL) in FORTRAN for microcomputer which yields the same values as Bertz's formulas. It is applied to a number of examples as well as to all four-, five-, and six-carbon skeletons to evaluate its validity. The formulas are well adapted for use in locating synthesis pathways with least molecular complexity in our synthesis program.