FZG gear testing is widely used to evaluate the performance of lubricants, gear materials, and gear-tooth geometries under different loads. During these tests, gear tooth wear results in the loss of gear profile in the form of micro-pitting, pitting and scuffing, can be observed. However, gear wear is usually measured by weighting. This method cannot be used to study the wear depth on a specific point on the gear-tooth surface. In this study, tooth profiles were measured via a profilometer during the FZG gear-pitting test. Moreover, an algorithm was developed to quantitatively evaluate the distributed cumulative wear and wear progress at a certain test stage. Simultaneously, the real tooth profile was obtained. Experiments were performed to validate the proposed method, and the results showed that gear-tooth-surface wear can be quantitatively determined. Thus, the proposed method can be used for further gear-failure-prediction experiments. •Gear tooth profiles are measured via a profilometer during FZG gear-pitting tests.•No wear region on the profiles are used in orthogonal-distance regression.•Distributed cumulative wear and wear at various test stages are quantitatively evaluated.•The method is experimentally validated and agrees with the previous simulation.