A thin M10 nut is 5.0 mm tall; a nylon-insert one is 12.5 mm. Both are sold as an M10 nut, both thread onto the same bolt, and nothing stamped on either says how much thread is inside it. That height is the m column of four different standards, and this page reads them against each other.
Four heights for one thread
| Size | Pitch (mm) | Thin m (mm) | Regular m (mm) | Flange m (mm) | Insert m (mm) |
|---|---|---|---|---|---|
| M4 | 0.70 | 2.2 | 3.2 | — | 5.0 |
| M5 | 0.80 | 2.7 | 4.7 | 5.0 | 6.0 |
| M6 | 1.00 | 3.2 | 5.2 | 6.0 | 7.5 |
| M8 | 1.25 | 4.0 | 6.8 | 8.0 | 9.5 |
| M10 | 1.50 | 5.0 | 8.4 | 10.0 | 12.5 |
| M12 | 1.75 | 6.0 | 10.8 | 12.0 | 15.0 |
| M14 | 2.00 | 7.0 | 12.8 | 14.0 | 17.0 |
| M16 | 2.00 | 8.0 | 14.8 | 16.0 | 19.0 |
| M18 | 2.50 | 9.0 | 15.8 | — | 21.0 |
| M20 | 2.50 | 10.0 | 18.0 | 20.0 | 22.0 |
| M22 | 2.50 | 11.0 | 19.4 | — | — |
| M24 | 3.00 | 12.0 | 21.5 | — | 26.0 |
Every value is that standard's own m column. For the insert nut m is the metal body only: its overall height, collar included, is a separate column and is 12.8 mm at M10 — 0.3 mm more. This page counts m for all four families, so the insert nut comes out understated rather than flattered.
The pitch column is shared. On every size that appears in more than one family, the standards print the same pitch, and that is what makes a millimetre of nut height comparable at all. If one family ever printed a different pitch, the turns below would stop measuring height and start measuring two things at once — so the build stops instead.
The 0.8 d rule holds only at the small end
The shorthand is that a regular nut is 0.8 d tall. Here that is exactly true on 4 of the 15 sizes — M2, M2.5, M3, M4 — which is precisely the smallest sizes in the standard. Above them the ratio runs 0.84 to 0.94: still close enough that the shorthand feels right, but no longer the number it names. The widest gap is M5: 4.7 mm of nut on a 5.0 mm thread, which is 0.94 d.
None of that is an error in the standard. The height is a step chosen for the bearing area and the socket, and 0.8 d is a shorthand that happens to land exactly on the small end. What the shorthand gets right is the order of magnitude. What it gets wrong is any calculation that depends on it — a nut height entered as 0.8 d is 0.04 d off on M10 alone.
The 0.5 d rule errs on the safe side
For thin nuts the shorthand is half the diameter. It holds exactly on 9 of the 12 sizes that standard covers. The 3 that miss are M4 (2.2 mm), M5 (2.7 mm), M6 (3.2 mm), and every one of them is taller than half the diameter, not shorter. The rule understates the part instead of overstating it: reserve space with 0.5 d and you reserve slightly too little, estimate engagement with it and you estimate slightly low.
What the height buys is turns
| Size | Thin (turns) | Regular (turns) | Flange (turns) | Insert (turns) |
|---|---|---|---|---|
| M4 | 3.14 | 4.57 | — | 7.14 |
| M5 | 3.38 | 5.88 | 6.25 | 7.50 |
| M6 | 3.20 | 5.20 | 6.00 | 7.50 |
| M8 | 3.20 | 5.44 | 6.40 | 7.60 |
| M10 | 3.33 | 5.60 | 6.67 | 8.33 |
| M12 | 3.43 | 6.17 | 6.86 | 8.57 |
| M14 | 3.50 | 6.40 | 7.00 | 8.50 |
| M16 | 4.00 | 7.40 | 8.00 | 9.50 |
| M18 | 3.60 | 6.32 | — | 8.40 |
| M20 | 4.00 | 7.20 | 8.00 | 8.80 |
| M22 | 4.40 | 7.76 | — | — |
| M24 | 4.00 | 7.17 | — | 8.67 |
A turn here is m ÷ pitch — the number of full turns of thread the nut contains. On every size where all four families appear, the order is strict: thin, then regular, then flange, then insert. Height is the only variable in that column, which is why the ordering never flips.
Across the whole table the thin nuts carry 3.14–4.40 turns and the regular ones 4.00–7.76 turns. On M10 the difference is concrete: 3.33 turns against 5.60, which is 2.3 fewer turns for 3.4 mm less height. A jam nut is not a short version of the same nut; it is a nut with less thread in it.
Where the standard number changes nothing
Four pairs in this database are identical row for row: ISO 4035 / DIN 439, ISO 4032 / DIN 934, ISO 4161 / DIN 6923, ISO 10511 / DIN 985. Same sizes, same width across flats, same m. If you have been treating them as two parts that might differ, this page cannot tell them apart — the DIN vs ISO guide covers where the two systems do diverge.
Where this stops
- Strength. Nothing here measures it. Turns are geometry, m ÷ pitch, and a thin nut with fewer turns is not "weaker by a fixed percentage" — how much load a thread carries depends on the material, the property class and the engagement, none of which is in these four tables. Do not read the second table as a strength ranking.
- The insert nut's collar. Counting from
munderstates it by 0.3 mm at M10, and by more on the larger sizes, where the collar is thicker. - Other nut styles. These four families are what the database holds. Weld nuts, cap nuts and slotted nuts are not in it, and neither are thin nuts above M24.
- Which one to buy. This page compares heights and counts turns. It does not know your joint, your preload or your space, and it makes no recommendation.
The four standards are on the site as data pages — ISO 4035, ISO 4032, ISO 4161 and ISO 10511 — and the nuts index lists every size this database carries.