About

In hardware distribution and mechanical inventory, washers are rarely counted by hand; they are sold and measured by weight. However, end-users often need specific counts. The density and dimensions of washers vary significantly between standards. A 1/2-inch USS (United States Standard) washer is thicker and wider than a 1/2-inch SAE (Society of Automotive Engineers) washer, meaning a pound of SAE washers contains nearly double the quantity of USS washers.

This tool utilizes a comprehensive database of standard steel washer weights to provide accurate quantity estimates from bulk weight inputs, covering the most common industrial standards.

Formulas

The calculator uses the "Weight per 100 pieces" standard often found in fastener catalogs. The logic normalizes this to a single unit weight.

Count = Weight_total × 100Weight_{per_100}

Reference Data

Bolt Size	Type	Weight (lbs/100pcs)	Pcs/lb (Approx)
1/4"	SAE	0.67	149
1/4"	USS	0.82	121
3/8"	SAE	1.49	67
3/8"	USS	1.49	67
1/2"	SAE	1.85	54
1/2"	USS	3.85	26
5/8"	SAE	2.85	35
5/8"	USS	7.65	13
3/4"	SAE	4.55	22
3/4"	USS	11.00	9

Frequently Asked Questions

USS (United States Standard) washers have a larger outer diameter and are generally thicker, designed for coarse thread bolts. SAE (Society of Automotive Engineers) washers have a smaller outer diameter and are thinner, designed to fit tighter spaces often found in automotive applications.

Fender washers have a much larger outer diameter than both USS and SAE. This tool includes a specific category for Fender washers, as their weight is significantly higher, reducing the count per pound.

Steel thickness tolerances in stamping manufacturing can vary. A batch of washers rolled slightly thicker will result in a lower count per pound. Estimates are usually accurate within ±5%.