How to Judge a Belt Size

An automotive belt is designed to operate engine accessories such as the alternator, power steering pump, air conditioner compressor and water pump. Belts come in a couple of forms, including basic drive belts and serpentine belts. As the engine is running, the belt travels around the pulleys of the engine accessories. As the belt turns around the pulleys, it enables each accessory to function. If the belt becomes damaged, it can be measured for replacement while it is still routed around the accessory pulleys.

Instructions

1

Open the hood of the vehicle and lock it in place. Inspect the top of the fan shroud and locate the belt routing diagram. All vehicles have a belt routing diagram that gives the exact routing instructions for the belt. If the diagram is not on top of the fan shroud, check on the underside of the hood.

2

Locate the belt in need of replacement. Find an easy-to-reach area on the top side of the belt. Tape one end of the the 10-foot piece of string to the top side of the belt with the masking tape. Use a couple pieces of tape if necessary to prevent the string from slipping.

3

Inspect the belt routing direction on the belt routing diagram. Pull the string around the accessory pulleys in the same routing direction as explained by the routing diagram. When this end of the string has reached the taped end, overlap the two ends and mark the string in the exact area where it meets the taped end.

4

Remove the taped end of the string from the belt. Pull the string out of the engine compartment and lay the string out flat on the floor or the ground. Use a flexible metric tape measure to measure the string from the taped end to the marked location on the other end of the string. The final measurement from the taped end to the marked location on the other end of the string will be the exact measurement of the belt.

5

Write down the measurement of the belt and use this measurement when buying a new belt.