Metric Hex Nut Dimensions Chart (ISO 4032 / DIN 934)

Wrench size, corner width and height of every standard metric hex nut to ISO 4032, M1.6 to M64 — and the four sizes where old DIN 934 nuts differ.

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A metric hex nut is described by its thread (for example M12 × 1.75) and three dimensions: the width across flats s, which is the spanner size; the width across corners e, which decides socket and clearance space; and the height m. The table lists those dimensions for regular (style 1) nuts to ISO 4032, the international standard that replaced Germany's DIN 934. For most sizes the two are interchangeable, but at M10, M12, M14 and M22 the spanner size differs — an M12 ISO nut takes an 18 mm spanner, an M12 DIN 934 nut a 19 mm one. All dimensions are in millimetres; s and m are maximum values, e is the minimum.

ISO 4032 regular hex nuts (style 1)

s = width across flats (spanner size, max), e = width across corners (min), m = nut height (max). Coarse thread pitch. All in mm. M14, M18, M22, M27, M33, M39, M45, M52 and M60 are second-choice sizes.

Thread	Pitch (mm)	s — flats (mm)	e — corners (mm)	m — height (mm)
M1.6	0.35	3.2	3.41	1.3
M2	0.4	4	4.32	1.6
M2.5	0.45	5	5.45	2.0
M3	0.5	5.5	6.01	2.4
M4	0.7	7	7.66	3.2
M5	0.8	8	8.79	4.7
M6	1	10	11.05	5.2
M8	1.25	13	14.38	6.8
M10	1.5	16	17.77	8.4
M12	1.75	18	20.03	10.8
M14	2	21	23.36	12.8
M16	2	24	26.75	14.8
M18	2.5	27	29.56	15.8
M20	2.5	30	32.95	18.0
M22	2.5	34	37.29	19.4
M24	3	36	39.55	21.5
M27	3	41	45.20	23.8
M30	3.5	46	50.85	25.6
M33	3.5	50	55.37	28.7
M36	4	55	60.79	31.0
M39	4	60	66.44	33.4
M42	4.5	65	71.30	34.0
M45	4.5	70	76.95	36.0
M48	5	75	82.60	38.0
M52	5	80	88.25	42.0
M56	5.5	85	93.56	45.0
M60	5.5	90	99.21	48.0
M64	6	95	104.86	51.0

28 rows

Where DIN 934 differs from ISO 4032

DIN 934 was withdrawn but is still printed on drawings and stocked by suppliers. Check the spanner size before ordering tools or designing a recess.

Thread	ISO 4032 spanner (mm)	DIN 934 spanner (mm)
M10	16	17
M12	18	19
M14	21	22
M22	34	32

4 rows

Why ISO nuts are taller

DIN 934 nuts are about 0.8 × the thread diameter high — an M12 is 10 mm. When the standard was revised into ISO 4032 the nuts were made taller (M12: 10.8 mm) so that, with matching property classes, the bolt breaks before the nut thread strips. The same rule decides the nut class: a class 8 nut with an 8.8 bolt, class 10 with 10.9, class 12 with 12.9. A higher-class nut on a lower-class bolt is fine; the reverse is not.

Reading the table: two quick uses

Which spanner for an M12 nut? 18 mm for an ISO 4032 nut, 19 mm if it is an older DIN 934 nut. A 19 mm spanner on an 18 mm nut will round its corners.
How much room does an M20 nut need to turn? Its corner width e is 32.95 mm, so a socket needs roughly 33 mm plus its wall thickness; on a flange, leave at least that diameter clear around each bolt centre.

What about M40, M7 or M9?

There is no M40 coarse thread in the ISO metric series used for hex nuts: the series goes M36, M39, M42, M45, M48. M40 nuts exist only as special or fine-thread parts, so their dimensions come from the supplier's drawing. The same applies to M7 and M9.

By O.E. — Partner, chairman of the board and CEO of a metal products manufacturer for 21 years; the company exports to 45 countries.

Drafted with AI assistance; calculations checked against primary sources and tested with the site's own code. About FlowUtil

Last reviewed October 30, 2026

About the Metric Hex Nut Dimensions Chart

Sources

Classification: Standard nut dimensions

Sources

ISO 4032 — Fasteners — Hexagon regular nuts (style 1)
ISO
DIN 934 — Hexagon nuts (withdrawn; superseded by ISO 4032)
DIN

Width across flats (maximum), width across corners (minimum) and nut height (maximum) are ISO 4032 values for M1.6 to M64, read from a fastener supplier's reproduction of the standard. The DIN 934 spanner sizes for M10, M12, M14 and M22 come from supplier product data. Confirm against the current edition of ISO 4032 for procurement.

How it was compiled

ISO 4032 defines regular (style 1) hex nuts. Its width across flats matches the corresponding ISO hex bolts (ISO 4014 / ISO 4017), so a single spanner fits both; the nut height is set so that a nut of matching property class develops the bolt's strength. ISO 4032 differs from the older DIN 934 in the spanner size of four threads and in nut height.

How current it is

Classification: Stable (mature standard)

ISO 4032 dimensions have been stable for decades; DIN 934 parts remain in circulation. Confirm the current edition for procurement.

Limitations

Dimensions cover regular hex nuts only; thin nuts, high nuts (style 2), flange nuts and prevailing-torque lock nuts follow separate standards.
Nut and bolt property classes must match: class 8 with 8.8, class 10 with 10.9, class 12 with 12.9.
Width across flats is a maximum; manufacturing tolerances apply.

Using it

Use width across flats to select the spanner; check whether the part is ISO 4032 or DIN 934 at M10, M12, M14 and M22.
Use width across corners for socket clearance and the space around a bolt on a flange.
For locking or vibration service, select the appropriate lock-nut standard rather than a standard hex nut.

Units and notation

All dimensions in millimetres. Width across corners is the diagonal used for socket clearance.

Frequently Asked Questions

What is the wrench size for an M10 nut?

16 mm for an ISO 4032 nut and 17 mm for an older DIN 934 nut.

Is DIN 934 the same as ISO 4032?

No. The dimensions match for most sizes, but the spanner size differs at M10, M12, M14 and M22, and DIN 934 nuts are lower (about 0.8 × the thread diameter). DIN 934 has been withdrawn; ISO 4032 replaced it.

What are the dimensions of an M3 nut?

ISO 4032: 5.5 mm across flats, 6.01 mm across corners (minimum), 2.4 mm high, 0.5 mm thread pitch.

How tall is a standard M20 nut?

18.0 mm maximum to ISO 4032; it takes a 30 mm spanner.

What is width across corners used for?

Clearance: it is the largest diameter the nut sweeps when it turns, so it sets socket size and the space needed around a bolt.

Can I use a higher property class nut with a lower class bolt?

Yes — the bolt remains the weak link, which is acceptable. Never use a lower-class nut than the bolt, as the thread may strip before the bolt reaches its proof load.

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