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High Hex Nut Dimensions (ISO 4033 Style 2, M5 to M36)

Guide · Updated October 28, 2026

ISO 4033 covers hexagon high nuts, style 2: a plain hex nut with the same wrench size as ISO 4032 but a taller body. The table gives coarse pitch, width across flats s (wrench size) max and min, nut height m max and min, wrenching height mw min, width across corners e min and bearing face dw min. Values agree between the ISO 4033:2023 preview tables, the ISO 4033:2012 table on GlobalFastener and the BS EN ISO 4033 table on EngineersEdge (one EngineersEdge e min typo at M14, 23.35, is outvoted by 23.36). The 2023 edition gives mw and dw to two decimals, so small rounding differences such as 10.7 vs 10.72 are shown at the precision all sources share. Note on M5 dw: the 2012 edition lists 6.9 mm and the 2023 edition changed it to 7.20 mm, so it is left out. The 2023 edition also adds M7, M18, M22, M27, M33 and M39, not listed here.

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Step by step

  1. Match the thread: Check diameter and pitch with a thread gage. This chart is coarse pitch M5 to M36.
  2. Pick the wrench: Across flats s is the same as an ISO 4032 style 1 nut: M6 10 mm, M8 13 mm, M10 16 mm, M12 18 mm, M16 24 mm.
  3. Check the height: A style 2 nut is about 10 percent taller than style 1. Use m max for clearance in pockets and under covers.
  4. Know why it is taller: The extra height gives more thread engagement, so the nut strips less easily. It is common in property class 9 and 12 and in high strength joints.
  5. Leave thread past the nut: Run at least 2 full threads past the nut face.
  6. Match the property class: Pair the nut class with the bolt class, for example class 10 or 12 nut with a 10.9 or 12.9 bolt.

ISO 4033 high hex nut dimensions (mm)

Columns: thread size, coarse pitch P, width across flats s max and min (s max is the wrench size), nut height m max, m min, wrenching height mw min, width across corners e min, bearing face diameter dw min. Grade A through M16, grade B above. M14 is a second choice size.

Style 2 vs style 1 height

Nut height m max, ISO 4033 style 2 vs ISO 4032 style 1: M6 5.70 vs 5.20 mm, M8 7.50 vs 6.80 mm, M10 9.30 vs 8.40 mm, M12 12.00 vs 10.80 mm, M16 16.40 vs 14.80 mm. Same wrench, taller nut.

Worked example: bolt length for an M12 high nut

Clamping two 10 mm plates with one 2.5 mm ISO 7089 washer: grip 22.5 mm, nut m max 12.00 mm, plus 2 threads at 1.75 mm = 3.5 mm. Total 38 mm, so an M12 x 40 works.

Common problems

FAQ

What is the difference between ISO 4032 and ISO 4033?

Both are regular hex nuts with the same wrench size. ISO 4033 is style 2, a taller nut. For example M10 is 8.40 mm max high in ISO 4032 and 9.30 mm max in ISO 4033.

What wrench fits an M12 ISO 4033 nut?

18 mm, the same as an ISO 4032 nut. Older DIN 934 nuts used 19 mm at M12.

Is ASME B18.2.4.2M the same as ISO 4033?

The ASME metric style 2 hex nut standard follows the same main dimensions as ISO 4033. Check the drawing or supplier sheet for a specific part.

How tall is an M16 high nut?

15.70 mm min to 16.40 mm max, about equal to the thread diameter.

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