Dimensions mm · values as the standard states them Size P s e k r a1 dp k´ z1 M5 0.8 5
4.82 – 5
6.5
5.92 – 6.5
5
≥ 0.2
≤ 2.4
3.5
3.32 – 3.5
≥ 3.4
1.25
M6 1 6
5.82 – 6
8
7.42 – 8
6
≥ 0.25
≤ 3
4
3.82 – 4
≥ 4.1
1.5
M8 1.25 8
7.78 – 8
10
9.42 – 10
8
≥ 0.4
≤ 4
5.5
5.32 – 5.5
≥ 5.5
2
M10 1.5 10
9.78 – 10
13
12.3 – 13
10
≥ 0.4
≤ 4.5
7
6.78 – 7
≥ 6.9
2.5
M12 1.75 13
12.73 – 13
17
16.3 – 17
12
≥ 0.6
≤ 5.3
8.5
8.28 – 8.5
≥ 8.3
3
M16 2 17
16.73 – 17
22
21.16 – 22
16
≥ 0.6
≤ 6
12
11.73 – 12
≥ 11.1
4
M20 2.5 22
21.67 – 22
28
27.16 – 28
20
≥ 0.8
≤ 7.5
15
14.73 – 15
≥ 13.8
5
2.3 – 5
M24 3 24
23.67 – 24
32
31 – 32
22
≥ 0.8
≤ 9
18
17.78 – 18
≥ 15.2
6
Ranges read min – max; ≤ / ≥ where the standard gives one limit, ≈ for approximate values. Sizes in (brackets) are non-preferred. Select a row for its size sheet.
Length tolerances 8 7.71 – 8.29
10 9.71 – 10.29
16 15.65 – 16.35
20 19.58 – 20.42
25 24.58 – 25.42
30 29.58 – 30.42
35 34.5 – 35.5
40 39.5 – 40.5
45 44.5 – 45.5
50 49.5 – 50.5
55 54.4 – 55.6
60 59.4 – 60.6
70 69.4 – 70.6
80 79.4 – 80.6
90 89.3 – 90.7
100 99.3 – 100.7
110 109.3 – 110.7
120 119.3 – 120.7
140 139.2 – 140.8
Size sheet · DIN 479
M5
s width across flats 5
e width across corners 6.5
k head height 5
r fillet radius ≥ 0.2
a1 length undercut ≤ 2.4
dp diameter of the ejector 3.5
k´ minimum size of the head on the key ≥ 3.4
z1 length of the ejector 1.25 Thread · ISO 261/262
Pitch P 0.8
d2 4.48
d3 4.019
Tap drill 4.2
Stress area As 14.18 mm² Standard lengths
8 · 10 · 16 · 20 · 25 · 30 · 35 · 40
Size sheet · DIN 479
M6
s width across flats 6
e width across corners 8
k head height 6
r fillet radius ≥ 0.25
a1 length undercut ≤ 3
dp diameter of the ejector 4
k´ minimum size of the head on the key ≥ 4.1
z1 length of the ejector 1.5 Thread · ISO 261/262
Pitch P 1
d2 5.35
d3 4.773
Tap drill 5
Stress area As 20.12 mm² Standard lengths
8 · 10 · 16 · 20 · 25 · 30 · 35 · 40 · 45
Size sheet · DIN 479
M8
s width across flats 8
e width across corners 10
k head height 8
r fillet radius ≥ 0.4
a1 length undercut ≤ 4
dp diameter of the ejector 5.5
k´ minimum size of the head on the key ≥ 5.5
z1 length of the ejector 2 Thread · ISO 261/262
Pitch P 1.25
d2 7.188
d3 6.466
Tap drill 6.75
Stress area As 36.61 mm² Standard lengths
10 · 16 · 20 · 25 · 30 · 35 · 40 · 45 · 50 · 55
Size sheet · DIN 479
M10
s width across flats 10
e width across corners 13
k head height 10
r fillet radius ≥ 0.4
a1 length undercut ≤ 4.5
dp diameter of the ejector 7
k´ minimum size of the head on the key ≥ 6.9
z1 length of the ejector 2.5 Thread · ISO 261/262
Pitch P 1.5
d2 9.026
d3 8.16
Tap drill 8.5
Stress area As 57.99 mm² Standard lengths
16 · 20 · 25 · 30 · 35 · 40 · 45 · 50 · 55 · 60
Size sheet · DIN 479
M12
s width across flats 13
e width across corners 17
k head height 12
r fillet radius ≥ 0.6
a1 length undercut ≤ 5.3
dp diameter of the ejector 8.5
k´ minimum size of the head on the key ≥ 8.3
z1 length of the ejector 3 Thread · ISO 261/262
Pitch P 1.75
d2 10.863
d3 9.853
Tap drill 10.25
Stress area As 84.27 mm² Standard lengths
20 · 25 · 30 · 35 · 40 · 45 · 50 · 55 · 60 · 70 · 80 · 90
Size sheet · DIN 479
M16
s width across flats 17
e width across corners 22
k head height 16
r fillet radius ≥ 0.6
a1 length undercut ≤ 6
dp diameter of the ejector 12
k´ minimum size of the head on the key ≥ 11.1
z1 length of the ejector 4 Thread · ISO 261/262
Pitch P 2
d2 14.701
d3 13.546
Tap drill 14
Stress area As 156.67 mm² Standard lengths
40 · 45 · 50 · 55 · 60 · 70 · 80 · 90 · 100 · 110 · 120
Size sheet · DIN 479
M20
s width across flats 22
e width across corners 28
k head height 20
r fillet radius ≥ 0.8
a1 length undercut ≤ 7.5
dp diameter of the ejector 15
k´ minimum size of the head on the key ≥ 13.8
z1 length of the ejector 5 Thread · ISO 261/262
Pitch P 2.5
d2 18.376
d3 16.933
Tap drill 17.5
Stress area As 244.79 mm² Standard lengths
50 · 55 · 60 · 70 · 80 · 90 · 100 · 110 · 120 · 140
Size sheet · DIN 479
M24
s width across flats 24
e width across corners 32
k head height 22
r fillet radius ≥ 0.8
a1 length undercut ≤ 9
dp diameter of the ejector 18
k´ minimum size of the head on the key ≥ 15.2
z1 length of the ejector 6 Thread · ISO 261/262
Pitch P 3
d2 22.051
d3 20.319
Tap drill 21
Stress area As 352.5 mm² Standard lengths
55 · 60 · 70 · 80 · 90 · 100 · 110 · 120 · 140
Provenance
Draft — values taken from a single source and not yet cross-checked.
fasteners.eu dimensions, lengths, materials, property classes, current norm, equivalent norms Accessed 2026-09-23 · For design and safety-critical use, consult the current edition of the standard.
Data notes (1) 15 value(s) omitted after consistency checks: M5 k: min 5.15 > max 4.85 in source — min/max omitted; M5 z1: min 1.5 > max 1.25 in source — min/max omitted; M6 k: min 6.15 > max 5.85 in source — min/max omitted; M6 z1: min 1.75 > max 1.5 in source — min/max omitted; M8 k: min 8.18 > max 7.82 in source — min/max omitted; M8 z1: min 2.25 > max 2 in source — min/max omitted; M10 k: min 10.18 > max 9.82 in source — min/max omitted; M10 z1: min 2.75 > max 2.5 in source — min/max omitted; M12 k: min 12.21 > max 11.79 in source — min/max omitted; M12 z1: min 3.25 > max 3 in source — min/max omitted; M16 k: min 16.21 > max 15.79 in source — min/max omitted; M16 z1: min 4.3 > max 4 in source — min/max omitted …