How To Measure Chain Size For Sprocket. The pitch is the distance between rollers (1/2 on all modern bicycle chain). Measure from center to center of where the chain roller would set between the teeth that will give you the pitch.
It will affect the length of the chain run, and wheel base of your bike. Measure from the first to the third, then divide that. Sprocket size will affect chain length.
Then, divide that result by 2.
The pitch is the “chain size”. The first number (1/2) is the chain pitch; Motorcycle gearing sprockets rpm km/h: The sprocket size represents the first two digits in the chain designation.