How To Measure Belt Size Car. If you do not have an existing belt, measure around the top of your pants where the belt loops are and be sure to tighten the tape measure as tight as you would like your belt to be. Measure the length of string it took to wrap around the path of the serpentine belt.
Set the flat outer edge of the v belt on a flat surface. Belts are measured in inches and you should round to the nearest inch. Adjust to a slightly lesser length to ensure tightness when measuring an existing belt that has stretched.
With the alternator snugged in the desired position, the belt must be pulled tight and held still for accurate marking.
Measure the length of string it took to wrap around the path of the serpentine belt. For broken belts, simply measure the total length of the belt. Measure each individual band for banded belts to obtain the correct width. This distance is measured from the center of the crankshaft to the center of the jackshaft.