Hex Nut Sizes
Wrench size (across flats) and height for inch and metric hex nuts.
Across-flats is the wrench/socket size. Thickness is the nut height — the Bolt Length calculator uses it to size a bolt for a stack-up.
Inch hex nuts (ASME B18.2.2)
| Size | Across flats (in) | Thickness (in) |
|---|---|---|
| #4-40 | 0.25 | 0.094 |
| #6-32 | 0.3125 | 0.109 |
| #8-32 | 0.3438 | 0.125 |
| #10-24 | 0.375 | 0.13 |
| 1/4-20 | 0.4375 | 0.2188 |
| 5/16-18 | 0.5 | 0.2656 |
| 3/8-16 | 0.5625 | 0.3281 |
| 7/16-14 | 0.6875 | 0.375 |
| 1/2-13 | 0.75 | 0.4375 |
| 9/16-12 | 0.875 | 0.4844 |
| 5/8-11 | 0.9375 | 0.5469 |
| 3/4-10 | 1.125 | 0.6406 |
| 7/8-9 | 1.3125 | 0.75 |
| 1-8 | 1.5 | 0.8594 |
Metric hex nuts (ISO 4032)
| Size | Across flats (mm) | Thickness (mm) |
|---|---|---|
| M1.6 | 3.2 | 1.3 |
| M2 | 4 | 1.6 |
| M2.5 | 5 | 2 |
| M3 | 5.5 | 2.4 |
| M4 | 7 | 3.2 |
| M5 | 8 | 4.7 |
| M6 | 10 | 5.2 |
| M8 | 13 | 6.8 |
| M10 | 16 | 8.4 |
| M12 | 18 | 10.8 |
| M16 | 24 | 14.8 |
| M20 | 30 | 18 |