The pitch, also called the diametral pitch, indicates the number of teeth divided by the pitch diameter. (Pitch diameter measures the distance across the pitch circle, which intersects the meshing points on each of the gear’s teeth.) For example, a spur gear with 28 teeth and a pitch diameter of 2.8 inches would have a 10 pitch. The pitch also serves as a guide for tooth size: a 10-pitch spur gear will have more teeth than a 5-pitch spur gear with the same pitch diameter, but the 5-pitch gear’s teeth will be bigger. For two gears to work together, they must have the same pitch.