How To Calculate Gear Pitch

The diametral pitch of a gear describes how densely its teeth are set around it. The pitch is the ratio between the number of teeth and the gear's size, and engineers always express it as a whole number. This value is important for further calculations involving the gear, including the size of each of the gear's teeth. A smaller pitch corresponds with larger teeth, and smaller teeth belong on a gear with a larger pitch.

Step 1

Measure the radius of the gear. Exclude the gear's teeth from your measurement. For this example, imagine a gear with a radius of 3 inches.

Step 2

Multiply this measurement by 2: 3 × 2 = 6 inches.

Step 3

Divide the number of teeth on the gear by this measurement. For example, if the gear has 28 teeth: 28 / 6 = 4.67.

Step 4

Round this figure to the nearest whole number: 4.67 is approximately 5, so the gear has a pitch of 5.