Hex nut ISO 4032 and washer ISO 7089: dimensions
Published October 19, 2026 — ISO 4032 hex nut and ISO 7089 flat washer dimensions from M1.6 to M36, the spanner sizes that changed from DIN 934 and a bolt length calculator.
In short: an ISO 4032 hex nut is defined by its width across flats s and its height m: M6 → 10 mm spanner, M8 → 13, M10 → 16, M12 → 18, M16 → 24, M20 → 30. The matching ISO 7089 flat washer has a hole slightly larger than the bolt: M8 → 8.4 × 16 × 1.6 mm, M10 → 10.5 × 20 × 2 mm. Watch out for older DIN 934 nuts, whose spanner size differs for M10, M12, M14 and M22.
1. Calculator: nut, washer and bolt length
Pick the diameter, the clamped thickness and the number of washers. The calculator gives the spanner size, the ISO nut and washer, then the minimum bolt length (two pitches of protrusion) and the next standard length up.
2. ISO 4032 hex nut dimensions
Regular hex nuts (style 1), coarse metric thread. Dimensions in mm: s is the spanner size (width across flats), m the height, e the minimum width across corners. The most common sizes are in bold.
For the bolt clearance hole and the tap drill, see the metric thread chart; for tightening, the bolt torque chart.
3. ISO 7089 flat washer dimensions
Plain washers, normal series, product grade A, for bolts and nuts. Dimensions in mm: d1 is the hole diameter (minimum), d2 the outside diameter (maximum), h the nominal thickness and its range.
- The washer spreads the bearing load of the nut on a soft part or a slotted hole, and protects the surface during tightening.
- For a large clearance hole or an aluminium part, the large series (ISO 7093) has a bigger outside diameter; for a socket head cap screw, the small series (ISO 7092) fits under the head.
4. ISO 4032 vs DIN 934: the spanner sizes that change
DIN 934 was replaced by ISO 4032, but both are still found in stock. Only four sizes change spanner size (mm):
- ISO nuts are also taller than DIN ones: 8.4 mm vs 8 mm for M10, 10.8 vs 10 for M12. For the same bolt length, the protrusion is therefore slightly shorter.
- On a drawing or a bill of materials, write the full standard (ISO 4032 - M10 - 8): "M10 nut" alone does not say which spanner or which height to expect.
5. Bolt length to plan for with a nut
- L ≥ e + h + m + 2P: clamped thickness, washer(s), nut height and at least two pitches of protrusion, so that every thread of the nut is engaged. I recommend taking the next standard length up, without too much excess.
- Example: M10 (P = 1.5), two 10 mm plates, one washer: 20 + 2 + 8.4 + 3 = 33.4 mm, so a 35 mm bolt.
- A partially threaded bolt should keep its shank in the parts and its thread under the nut: check the thread length b of the chosen bolt, as for ISO 4762 socket head cap screws.
- The nut's property class must at least match the bolt's: class 8 nut for an 8.8 bolt, class 10 for a 10.9.
Printable version: the nut and washer charts as a PDF (A4, no sign-up), to keep in the workshop or at your desk.
6. FAQ
What spanner size for an M10 nut?
A 16 mm spanner for an ISO 4032 nut. Older DIN 934 M10 nuts take a 17 mm spanner, and both are still in stock. The same goes for M12 (18 in ISO, 19 in DIN), M14 (21 vs 22) and M22 (34 vs 32).
How thick is an M8 nut?
6.8 mm maximum for an ISO 4032 nut (6.44 mm minimum), with a 13 mm spanner. The equivalent DIN 934 nut is 6.5 mm. A thin (jam) nut is much thinner.
What size is an M8 washer?
An ISO 7089 M8 washer has an 8.4 mm hole, a 16 mm outside diameter and a 1.6 mm thickness. M10: 10.5 × 20 × 2; M12: 13 × 24 × 2.5.
What is the difference between ISO 4032 and DIN 934?
ISO 4032 replaced DIN 934. Spanner sizes change for M10, M12, M14 and M22, and ISO nuts are taller (for example 8.4 mm for M10 vs 8 mm). They are not interchangeable on a drawing: state the standard.
How long should a bolt be with a nut?
Add the clamped thickness, the washers, the nut height and a protrusion of at least two pitches, then take the next standard length up. For an M10 clamping 20 mm with one washer: 20 + 2 + 8.4 + 3 = 33.4 mm, so a 35 mm bolt.