How to Figure the Belt Size for a Riding Lawnmower

There are two belts on most riding lawnmowers. One belt connects the transmission of the lawn tractor to the driveshaft pulley and the other belt connects the mower deck to the driveshaft pulley. Both belts, usually made of Kevlar and of a V-groove construction, vary greatly in length on just about every make and model. When you belt wears out, you might wonder how to size the belt for replacement. Fortunately, there are two ways you can size the replacement belt for your mower.

Most mowers have at least two drive belts.

Broken Belt or Cutting Belt for Immediate Replacement

Step 1

Cut though the belt with a utility knife if the belt wore but did not break on its own and you do not require the use of your mower before you can replace the belt. If the belt is already broken, do not cut it.

Step 2

Stretch the belt out with its flat side resting on a flat surface such as a table or garage floor. If the belt tries to roll up on its own, weight each end with something heavy.

Step 3

Place the end of a tailor's tape measure at one end of the belt and extend it to the other end. Take a measurement from the tape measure to determine the overall length of the belt.

Measure the Belt for Future Replacement

Step 4

Place the belt onto a flat surface, such as a table or garage floor, so the belt rests on its flat side and conforms to the shape of a circle.

Step 5

Place a mark on the inner edge of the belt with chalk to mark the starting and ending point of your measurement. Position the mark on the tip of the V-groove on the belt.

Step 6

Place one end of the tailor's tape measure on the mark, then extend the tape measure around the inside circumference of the circle until you reach the mark with the other end of the tape measure. Take your reading from the tape measure to determine the size of the belt.