Flat Washer Size Chart (USS vs SAE)
Inside and outside diameters for USS (wide) and SAE (narrow) flat washers, plus the matching bolt size.
| Bolt size | USS ID (in) | USS OD (in) | SAE ID (in) | SAE OD (in) |
|---|---|---|---|---|
| 1/4 | 9/32 | 5/8 | 5/16 | 3/4 |
| 5/16 | 11/32 | 3/4 | 3/8 | 7/8 |
| 3/8 | 13/32 | 13/16 | 7/16 | 1 |
| 1/2 | 17/32 | 1-1/16 | 9/16 | 1-3/8 |
| 5/8 | 21/32 | 1-3/8 | 11/16 | 1-3/4 |
| 3/4 | 13/16 | 1-5/8 | 13/16 | 2 |
USS washers are wider and thicker for soft materials; SAE washers are narrower for hardened surfaces and tighter fits.
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