Heavy hex nut dimensions chart.
Heavy hex and heavy hex jam nuts from 1/4 to 4 in., with hex and hex jam nuts and ISO metric nuts: the wrench size, width across the flats and corners, and thickness, with the maximum and minimum the standard allows.
| Nominal size (in.) | Threads per inch (UNC) | Wrench size (in.) | F — width across flats | G — width across corners | H — nut thickness | H1 — heavy hex jam nut thickness | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Max. | Min. | Max. | Min. | Max. | Min. | |||
| 1/4" | 20 | 1/2 | 0.500 | 0.488 | 0.577 | 0.556 | 0.250 | 0.218 | 0.188 | 0.156 |
| 5/16" | 18 | 9/16 | 0.562 | 0.546 | 0.650 | 0.622 | 0.314 | 0.280 | 0.220 | 0.186 |
| 3/8" | 16 | 11/16 | 0.688 | 0.669 | 0.794 | 0.763 | 0.377 | 0.341 | 0.252 | 0.216 |
| 7/16" | 14 | 3/4 | 0.750 | 0.728 | 0.866 | 0.830 | 0.441 | 0.403 | 0.285 | 0.247 |
| 1/2" | 13 | 7/8 | 0.875 | 0.850 | 1.010 | 0.969 | 0.504 | 0.464 | 0.317 | 0.277 |
| 9/16" | 12 | 15/16 | 0.938 | 0.909 | 1.083 | 1.037 | 0.568 | 0.526 | 0.349 | 0.307 |
| 5/8" | 11 | 1-1/16 | 1.062 | 1.031 | 1.227 | 1.175 | 0.631 | 0.587 | 0.381 | 0.337 |
| 3/4" | 10 | 1-1/4 | 1.250 | 1.212 | 1.443 | 1.382 | 0.758 | 0.710 | 0.446 | 0.398 |
| 7/8" | 9 | 1-7/16 | 1.438 | 1.394 | 1.660 | 1.589 | 0.885 | 0.833 | 0.510 | 0.458 |
| 1" | 8 | 1-5/8 | 1.625 | 1.575 | 1.876 | 1.796 | 1.012 | 0.956 | 0.575 | 0.519 |
| 1-1/8" | 7 | 1-13/16 | 1.812 | 1.756 | 2.093 | 2.002 | 1.139 | 1.079 | 0.639 | 0.579 |
| 1-1/4" | 7 | 2 | 2.000 | 1.938 | 2.309 | 2.209 | 1.251 | 1.187 | 0.751 | 0.687 |
| 1-3/8" | 6 | 2-3/16 | 2.188 | 2.119 | 2.526 | 2.416 | 1.378 | 1.310 | 0.815 | 0.747 |
| 1-1/2" | 6 | 2-3/8 | 2.375 | 2.300 | 2.742 | 2.622 | 1.505 | 1.433 | 0.880 | 0.808 |
| 1-5/8" | 8 UN | 2-9/16 | 2.562 | 2.481 | 2.959 | 2.828 | 1.632 | 1.556 | 0.944 | 0.868 |
| 1-3/4" | 5 | 2-3/4 | 2.750 | 2.662 | 3.175 | 3.035 | 1.759 | 1.679 | 1.009 | 0.929 |
| 1-7/8" | 8 UN | 2-15/16 | 2.938 | 2.844 | 3.392 | 3.242 | 1.886 | 1.802 | 1.073 | 0.989 |
| 2" | 4.5 | 3-1/8 | 3.125 | 3.025 | 3.608 | 3.449 | 2.013 | 1.925 | 1.138 | 1.050 |
| 2-1/4" | 4.5 | 3-1/2 | 3.500 | 3.388 | 4.041 | 3.862 | 2.251 | 2.155 | 1.251 | 1.155 |
| 2-1/2" | 4 | 3-7/8 | 3.875 | 3.750 | 4.474 | 4.275 | 2.505 | 2.401 | 1.505 | 1.401 |
| 2-3/4" | 4 | 4-1/4 | 4.250 | 4.112 | 4.907 | 4.688 | 2.759 | 2.647 | 1.634 | 1.522 |
| 3" | 4 | 4-5/8 | 4.625 | 4.475 | 5.340 | 5.102 | 3.013 | 2.893 | 1.763 | 1.643 |
| 3-1/4" | 4 | 5 | 5.000 | 4.838 | 5.774 | 5.515 | 3.252 | 3.124 | 1.876 | 1.748 |
| 3-1/2" | 4 | 5-3/8 | 5.375 | 5.200 | 6.207 | 5.928 | 3.506 | 3.370 | 2.006 | 1.870 |
| 3-3/4" | 4 | 5-3/4 | 5.750 | 5.562 | 6.640 | 6.341 | 3.760 | 3.616 | 2.134 | 1.990 |
| 4" | 4 | 6-1/8 | 6.125 | 5.925 | 7.073 | 6.755 | 4.014 | 3.862 | 2.264 | 2.112 |
All dimensions in inches. Sizes marked 8 UN have no UNC thread and are threaded 8 UN. Wrench size = basic width across flats.
| Nominal size (in.) | Threads per inch (UNC) | Wrench size (in.) | F — width across flats | G — width across corners | H — nut thickness | H1 — hex jam nut thickness | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Max. | Min. | Max. | Min. | Max. | Min. | |||
| 1/4" | 20 | 7/16 | 0.438 | 0.428 | 0.505 | 0.488 | 0.226 | 0.212 | 0.163 | 0.150 |
| 5/16" | 18 | 1/2 | 0.500 | 0.489 | 0.577 | 0.557 | 0.273 | 0.258 | 0.195 | 0.180 |
| 3/8" | 16 | 9/16 | 0.563 | 0.551 | 0.650 | 0.628 | 0.337 | 0.320 | 0.227 | 0.210 |
| 7/16" | 14 | 11/16 | 0.688 | 0.675 | 0.794 | 0.768 | 0.385 | 0.365 | 0.260 | 0.240 |
| 1/2" | 13 | 3/4 | 0.750 | 0.736 | 0.866 | 0.840 | 0.448 | 0.427 | 0.323 | 0.302 |
| 9/16" | 12 | 7/8 | 0.875 | 0.861 | 1.010 | 0.982 | 0.496 | 0.473 | 0.324 | 0.301 |
| 5/8" | 11 | 15/16 | 0.938 | 0.922 | 1.083 | 1.051 | 0.559 | 0.535 | 0.387 | 0.363 |
| 3/4" | 10 | 1-1/8 | 1.125 | 1.088 | 1.299 | 1.240 | 0.665 | 0.617 | 0.446 | 0.398 |
| 7/8" | 9 | 1-5/16 | 1.312 | 1.269 | 1.516 | 1.447 | 0.776 | 0.724 | 0.510 | 0.458 |
| 1" | 8 | 1-1/2 | 1.500 | 1.450 | 1.732 | 1.653 | 0.887 | 0.831 | 0.575 | 0.519 |
| 1-1/8" | 7 | 1-11/16 | 1.688 | 1.631 | 1.949 | 1.859 | 0.999 | 0.939 | 0.639 | 0.579 |
| 1-1/4" | 7 | 1-7/8 | 1.875 | 1.812 | 2.165 | 2.066 | 1.094 | 1.030 | 0.751 | 0.687 |
| 1-3/8" | 6 | 2-1/16 | 2.062 | 1.994 | 2.382 | 2.273 | 1.206 | 1.138 | 0.815 | 0.747 |
| 1-1/2" | 6 | 2-1/4 | 2.250 | 2.175 | 2.598 | 2.480 | 1.317 | 1.245 | 0.880 | 0.808 |
| 1-5/8" | 8 UN | see note | 2.430 | 2.350 | 2.805 | 2.679 | 1.416 | 1.364 | 0.944 | 0.868 |
| 1-3/4" | 5 | 2-5/8 | 2.625 | 2.538 | 3.031 | 2.893 | 1.540 | 1.460 | 1.009 | 0.929 |
| 1-7/8" | 8 UN | 2-13/16 | 2.813 | 2.722 | 3.247 | 3.103 | 1.651 | 1.567 | 1.073 | 0.989 |
| 2" | 4.5 | 3 | 3.000 | 2.900 | 3.464 | 3.306 | 1.763 | 1.675 | 1.138 | 1.050 |
| 2-1/4" | 4.5 | 3-3/8 | 3.375 | 3.263 | 3.897 | 3.719 | 1.986 | 1.890 | 1.267 | 1.155 |
| 2-1/2" | 4 | 3-3/4 | 3.750 | 3.625 | 4.330 | 4.133 | 2.209 | 2.105 | 1.427 | 1.401 |
| 2-3/4" | 4 | 4-1/8 | 4.125 | 3.988 | 4.763 | 4.546 | 2.431 | 2.319 | 1.556 | 1.522 |
| 3" | 4 | 4-1/2 | 4.500 | 4.350 | 5.196 | 4.959 | 2.654 | 2.534 | 1.685 | 1.643 |
| 3-1/4" | 4 | 4-7/8 | 4.875 | 4.713 | 5.629 | 5.373 | 2.877 | 2.749 | 1.814 | 1.748 |
| 3-1/2" | 4 | 5-1/4 | 5.250 | 5.075 | 6.062 | 5.786 | 3.100 | 2.964 | 1.943 | 1.870 |
| 3-3/4" | 4 | 5-5/8 | 5.625 | 5.438 | 6.495 | 6.199 | 3.322 | 3.178 | 2.072 | 1.990 |
| 4" | 4 | 6 | 6.000 | 5.800 | 6.928 | 6.612 | 3.545 | 3.393 | 2.201 | 2.112 |
All dimensions in inches. Sizes marked 8 UN have no UNC thread and are threaded 8 UN. The standard prints 2.430 - 2.350 in. across the flats for the 1-5/8 hex nut, which is not a fractional wrench size, so none is given.
| Size | Pitch (mm) | Wrench size (mm) | s — width across flats | e — across corners | m — nut thickness | ||
|---|---|---|---|---|---|---|---|
| Max. | Min. | Min. | Max. | Min. | |||
| M5 | 0.8 | 8 | 8.00 | 7.78 | 8.79 | 4.70 | 4.40 |
| M6 | 1 | 10 | 10.00 | 9.78 | 11.05 | 5.20 | 4.90 |
| M8 | 1.25 | 13 | 13.00 | 12.73 | 14.38 | 6.80 | 6.44 |
| M10 | 1.5 | 16 | 16.00 | 15.73 | 17.77 | 8.40 | 8.04 |
| M12 | 1.75 | 18 | 18.00 | 17.73 | 20.03 | 10.80 | 10.37 |
| M14 | 2 | 21 | 21.00 | 20.67 | 23.36 | 12.80 | 12.10 |
| M16 | 2 | 24 | 24.00 | 23.67 | 26.75 | 14.80 | 14.10 |
| M18 | 2.5 | 27 | 27.00 | 26.16 | 29.56 | 15.80 | 15.10 |
| M20 | 2.5 | 30 | 30.00 | 29.16 | 32.95 | 18.00 | 16.90 |
| M22 | 2.5 | 34 | 34.00 | 33.00 | 37.29 | 19.40 | 18.10 |
| M24 | 3 | 36 | 36.00 | 35.00 | 39.55 | 21.50 | 20.20 |
| M27 | 3 | 41 | 41.00 | 40.00 | 45.20 | 23.80 | 22.50 |
| M30 | 3.5 | 46 | 46.00 | 45.00 | 50.85 | 25.60 | 24.30 |
| M33 | 3.5 | 50 | 50.00 | 49.00 | 55.37 | 28.70 | 27.40 |
| M36 | 4 | 55 | 55.00 | 53.80 | 60.79 | 31.00 | 29.40 |
| M39 | 4 | 60 | 60.00 | 58.80 | 66.44 | 33.40 | 31.80 |
| M42 | 4.5 | 65 | 65.00 | 63.10 | 71.30 | 34.00 | 32.40 |
| M45 | 4.5 | 70 | 70.00 | 68.10 | 76.95 | 36.00 | 34.40 |
| M48 | 5 | 75 | 75.00 | 73.10 | 82.60 | 38.00 | 36.40 |
| M52 | 5 | 80 | 80.00 | 78.10 | 88.25 | 42.00 | 40.40 |
| M56 | 5.5 | 85 | 85.00 | 82.80 | 93.56 | 45.00 | 43.40 |
| M60 | 5.5 | 90 | 90.00 | 87.80 | 99.21 | 48.00 | 46.40 |
| M64 | 6 | 95 | 95.00 | 92.80 | 104.86 | 51.00 | 49.10 |
All dimensions in mm, coarse thread. DIN 934 nuts differ across the flats at M10 (17), M12 (19), M14 (22) and M22 (32 mm); see the wrench size chart.
Dimensions from ASME B18.2.1-2012 and ASME B18.2.2-2015 as printed in the IFI Book of Fastener Standards (2018) and cross-checked against the IFI Technology Connection; metric from ISO 4014:2011, ISO 4032:2012, DIN 931 and DIN 934. Grades and the rest of each nut's data are on the product pages for heavy hex nuts, finished hex nuts and hex jam nuts.
Nut sizes: common questions.
What are the dimensions of a 1 inch heavy hex nut?
Per ASME B18.2.2-2015, a 1-8 heavy hex nut is 1-5/8 in. across the flats (1.625 to 1.575 in.), 1.876 to 1.796 in. across the corners, and 1.012 to 0.956 in. thick. The heavy hex jam nut is 0.575 to 0.519 in. thick.
What is the difference between a heavy hex nut and a hex nut?
A heavy hex nut is wider across the flats and thicker than a hex (finished hex) nut of the same thread. At 1 in. the heavy hex nut is 1-5/8 in. across the flats and 1.012 in. thick at most; the hex nut is 1-1/2 in. and 0.887 in. Heavy hex nuts are the usual partner for ASTM A193 B7 studs (A194 2H nuts) and structural bolts.
What size wrench for a 1/2 inch heavy hex nut?
7/8 in. A 7/8 in. heavy hex nut takes 1-7/16 in. See the wrench size chart for every size.
How thick is a heavy hex nut?
Close to its nominal thread diameter. A 1/2 in. heavy hex nut is 0.504 to 0.464 in. thick and a 1 in. nut 1.012 to 0.956 in.; the limits for every size are in the table.
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