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Metric Hex Nut Size Chart (ISO 4032, M3 to M36)

Guide · Updated October 28, 2026

ISO 4032 is the standard metric hex nut, style 1, product grade A up to M16 and grade B from M18. It replaced DIN 934. The table gives thread pitch, width across flats s (the wrench size), minimum width across corners e and nut height m from M3 to M36. Values agree between the ISO 4032:2023 and ISO 4032:1999 previews, the AmesWeb ISO 4032 chart and the Engineering Hardware ISO 4032 table. Check the current edition or your supplier for critical work.

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Step by step

Read the thread: Measure the bolt major diameter and check pitch with a thread pitch gage. M10 coarse is 1.5 mm; fine-thread nuts (ISO 8673) share the same s and m.
Find s: Width across flats s is the wrench size. ISO 4032 M10 is 16 mm, M12 is 18 mm, M14 is 21 mm and M22 is 34 mm.
Check height m: ISO 4032 is style 1. A taller style 2 nut (ISO 4033) or a thin jam nut (ISO 4035) changes m but not s.
Check corners e: e min is the smallest width across corners. Use it to size counterbores, wrench clearance and socket pockets.
Match the grade: Pair property class 8 nuts with 8.8 bolts and class 10 with 10.9. A weaker nut strips before the bolt yields.
Leave thread past the nut: Leave at least one to two full threads showing past the nut so it is fully engaged.

ISO 4032 hex nut dimensions (mm)

Columns are: thread size, coarse pitch P, s max (nominal wrench size), s min, e min, m max and m min. M14, M18, M22, M27 and M33 are non-preferred sizes. M3 and M4 come from Annex A of the 2023 edition (the main table of the 1999 edition).

Size | P | s max | s min | e min | m max | m min
M3 | 0.5 | 5.50 | 5.32 | 6.01 | 2.40 | 2.15
M4 | 0.7 | 7.00 | 6.78 | 7.66 | 3.20 | 2.90
M5 | 0.8 | 8.00 | 7.78 | 8.79 | 4.70 | 4.40
M6 | 1 | 10.00 | 9.78 | 11.05 | 5.20 | 4.90
M8 | 1.25 | 13.00 | 12.73 | 14.38 | 6.80 | 6.44
M10 | 1.5 | 16.00 | 15.73 | 17.77 | 8.40 | 8.04
M12 | 1.75 | 18.00 | 17.73 | 20.03 | 10.80 | 10.37
M14 | 2 | 21.00 | 20.67 | 23.36 | 12.80 | 12.10
M16 | 2 | 24.00 | 23.67 | 26.75 | 14.80 | 14.10
M18 | 2.5 | 27.00 | 26.16 | 29.56 | 15.80 | 15.10
M20 | 2.5 | 30.00 | 29.16 | 32.95 | 18.00 | 16.90
M22 | 2.5 | 34.00 | 33.00 | 37.29 | 19.40 | 18.10
M24 | 3 | 36.00 | 35.00 | 39.55 | 21.50 | 20.20
M27 | 3 | 41.00 | 40.00 | 45.20 | 23.80 | 22.50
M30 | 3.5 | 46.00 | 45.00 | 50.85 | 25.60 | 24.30
M33 | 3.5 | 50.00 | 49.00 | 55.37 | 28.70 | 27.40
M36 | 4 | 55.00 | 53.80 | 60.79 | 31.00 | 29.40

ISO 4032 vs DIN 934 wrench sizes

Most sizes kept the same wrench size when DIN 934 was replaced, but four changed. M10: 17 mm DIN, 16 mm ISO. M12: 19 mm DIN, 18 mm ISO. M14: 22 mm DIN, 21 mm ISO. M22: 32 mm DIN, 34 mm ISO. If a 17 mm wrench fits an M10 nut, it is an old DIN 934 or a JIS nut, not ISO 4032. ISO nuts are also taller (M10 8.4 mm vs 8 mm DIN) so the nut is stronger than the bolt at matching property class.

Related nut styles

ISO 4033 (style 2) uses the same s but a taller m, for example M10 at 9.3 mm and M12 at 12 mm. ISO 4035 thin (jam) nuts are about half height and are not rated for full bolt load. ISO 8673 fine-pitch nuts share the ISO 4032 s and m. Flange nuts (ISO 4161) add a bearing flange and often skip the washer.

Worked example: sizing a counterbore for a nut

A fixture needs an M8 nut recessed below the surface. e min is 14.38 mm, and a sharp hex would be 13.00 × 1.1547 = 15.01 mm across corners. A round counterbore must clear the corners, so cut at least 15.5 mm, or 16 mm to fit a socket of 13 mm with its wall. Depth: m max 6.80 mm plus 0.5 mm, call it 7.3 mm. For a captive hex pocket that stops rotation, mill 13.1 to 13.2 mm across flats instead.

Worked example: identifying a nut from the bin

A nut measures 15.9 mm across flats and 8.2 mm tall, and a 1.5 mm pitch gage fits. 15.9 is inside the 15.73 to 16.00 band and 8.2 is inside 8.04 to 8.40, so it is an ISO 4032 M10 style 1 nut. If it measured 16.9 mm flats and 8.0 mm tall it would be a DIN 934 M10.

Common problems

Wrench is sloppy on an M10: you are using 17 mm on an ISO 16 mm nut. Switch to 16 mm.
Nut strips before the bolt: nut class is lower than the bolt. Use class 8 with 8.8, 10 with 10.9.
Nut spins in a hex pocket: pocket was cut to e instead of s. Cut flats to s max plus a few tenths.
Nut will not start: pitch mismatch, often M10×1.25 fine vs M10×1.5 coarse. Check with a pitch gage.

FAQ

What size wrench fits an M10 nut?

16 mm for ISO 4032. Older DIN 934 M10 nuts are 17 mm, so keep both sizes on hand.

How thick is an M8 hex nut?

ISO 4032 M8 nut height m is 6.44 to 6.80 mm. A DIN 934 M8 nut is 6.5 mm nominal.

What is the difference between ISO 4032 and DIN 934?

DIN 934 was withdrawn and replaced by ISO 4032. Four sizes changed wrench size: M10 17→16, M12 19→18, M14 22→21 and M22 32→34. ISO nuts are also a little taller in most sizes.

What is e on a hex nut?

Width across corners. For a sharp hex it would be s ÷ cos 30° = 1.1547 × s; the standard gives e min a little lower because the corners are chamfered and the flats carry tolerance.

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