When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Take a piece of string and measure the distance you need and take that measurement to the auto parts store.
Yea use the string and the stock belt part number for reference. The parts store guys should be able to determine the length difference in the belt by the part number. Then you will be sure you have the right ribbed belt. I used my stock belt, measured how much I needed it shorter, then went to the parts store with my measurement and the stock belt part number.