The Bolt Depot’s washer size chart has two accompanying diagrams that you can use to read the chart. The chart lists the measurements of the inside diameter, outside diameter and thickness for different washer sizes. Use the accompanying images what parts of the washer the inside diameter, outside diameter and thickness corresponds to. The Alma Bolt Company & Prime Fasteners has a washer size chart on its website that shows these measurements are in inches.
To find the measurements for a specific washer size, look up the size in the first column of the chart. Next read across the same row to find the internal and external diameter and the thickness measurements. Both the Bolt Depot and the Alma Bolt Company & Prime Fasteners list measurements for the United States Standard and the Society of Automotive Engineers washers. Several of the USS and SAE washers have the same size number, but the measurements of each washer are different.
The design of the USS washer meets the requirements of the manufacturing, industrial and maintenance sectors, while the SAE washer came into existence to fulfill the needs of the automotive industry. SAE washers have a smaller outer diameter and are less thick than corresponding USS washers.