A simple and robust technique for absolute phase measurement based on number theory is presented. The new, to our knowledge, technique, which is compared with the Gushov-Solodkin algorithm, surmounts the shortcomings in the Gushov-Solodkin algorithm. The technique permits the three-dimensional shape measurement of objects that have discontinuous height steps and has resulted in a new and more powerful method of measuring surface absolute profile. Experimental results are presented that demonstrate the validity of the principle.