There are lots of reasons you need to know hex nut dimensions. You need to hex nut height to determine the best length of a fastener in a bolted assembly. You need to know the size of the hex to make sure you have sufficient clearance for the nut itself, the washer and a wrench.
| Size | Across Flats* | Height | ||||
|---|---|---|---|---|---|---|
| Hex Nut | Machine Screw Nut | Hex Nut | Jam Nut | Nylock Nut | Machine Screw Nut | |
| 0 | – | 5/32 | – | – | – | 3/64 |
| 1 | – | 5/32 | – | – | – | 3/64 |
| 2 | – | 3/16 | – | – | 9/64 | 1/16 |
| 3 | – | 3/16 | – | – | 9/64 | 1/16 |
| 4 | – | 1/4 | – | – | 9/64 | 3/32 |
| 6 | – | 5/16 | – | – | 11/64 | 7/64 |
| 8 | – | 11/32 | – | – | 15/64 | 1/8 |
| 10 | – | 3/8 | – | – | 15/64 | 1/8 |
| 12 | – | 7/16 | – | – | 5/16 | 5/32 |
| 1/4 | 7/16 | 7/16 | 7/32 | 5/32 | 5/16 | 3/16 |
| 5/16 | 1/2 | 9/16 | 17/64 | 3/16 | 11/32 | 7/32 |
| 3/8 | 9/16 | 5/8 | 21/64 | 7/32 | 29/64 | 1/4 |
| 7/16 | 11/16 | – | 3/8 | 1/4 | 29/64 | – |
| 1/2 | 3/4 | – | 7/16 | 5/16 | 19/32 | – |
| 9/16 | 7/8 | – | 31/64 | 5/16 | 41/64 | – |
| 5/8 | 15/16 | – | 35/64 | 3/8 | 3/4 | – |
| 3/4 | 1-1/8 | – | 41/64 | 27/64 | 7/8 | – |
| 7/8 | 1-5/16 | – | 3/4 | 31/64 | 63/64 | – |
| 1 | 1-1/2 | – | 55/64 | 35/64 | 1-3/64 | – |
| * This is also the size of wrench to use. | ||||||