Dimensions mm · values as the standard states them Size P s e k r a1 dp l form B z2 M6 1 8
8.79
5
0.25
3
4
10 – 40
3
M8 1.25 10
11.05
6
0.4
3.75
5.5
12 – 50
4
M10 1.5 13
14.38
7
0.4
4.5
7
16 – 80
5
M12 1.75 16
17.77
9
0.6
5.25
8.5
25 – 120
6
M16 2 18
19.92
11
0.6
6
12
30 – 200
8
M20 2.5 24
26.75
14
0.8
7.5
15
40 – 200
10
M24 3 30
33.53
17
0.8
9
18
45 – 200
12
M30 3.5 36
39.98
21
1
10.5
23
60 – 200
15
M36 4 46
51.28
25
1
12
28
60 – 200
18
M42 4.5 55
61.31
30
1.2
13.5
32
80 – 260
21
M48 5 65
72.61
34
1.6
15
38
90 – 300
24
M56 5.5 75
83.91
40
2
16.5
45
100 – 300
28
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.
Size sheet · DIN 561 B
M6
s width across flats 8
e width across corners 8.79
k head height 5
r fillet radius 0.25
a1 3
dp 4
l length of bolt (form B) 10 – 40
z2 3 Thread · ISO 261/262
Pitch P 1
d2 5.35
d3 4.773
Tap drill 5
Stress area As 20.12 mm² Size sheet · DIN 561 B
M8
s width across flats 10
e width across corners 11.05
k head height 6
r fillet radius 0.4
a1 3.75
dp 5.5
l length of bolt (form B) 12 – 50
z2 4 Thread · ISO 261/262
Pitch P 1.25
d2 7.188
d3 6.466
Tap drill 6.75
Stress area As 36.61 mm² Size sheet · DIN 561 B
M10
s width across flats 13
e width across corners 14.38
k head height 7
r fillet radius 0.4
a1 4.5
dp 7
l length of bolt (form B) 16 – 80
z2 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 Size sheet · DIN 561 B
M12
s width across flats 16
e width across corners 17.77
k head height 9
r fillet radius 0.6
a1 5.25
dp 8.5
l length of bolt (form B) 25 – 120
z2 6 Thread · ISO 261/262
Pitch P 1.75
d2 10.863
d3 9.853
Tap drill 10.25
Stress area As 84.27 mm² Size sheet · DIN 561 B
M16
s width across flats 18
e width across corners 19.92
k head height 11
r fillet radius 0.6
a1 6
dp 12
l length of bolt (form B) 30 – 200
z2 8 Thread · ISO 261/262
Pitch P 2
d2 14.701
d3 13.546
Tap drill 14
Stress area As 156.67 mm² Size sheet · DIN 561 B
M20
s width across flats 24
e width across corners 26.75
k head height 14
r fillet radius 0.8
a1 7.5
dp 15
l length of bolt (form B) 40 – 200
z2 10 Thread · ISO 261/262
Pitch P 2.5
d2 18.376
d3 16.933
Tap drill 17.5
Stress area As 244.79 mm² Size sheet · DIN 561 B
M24
s width across flats 30
e width across corners 33.53
k head height 17
r fillet radius 0.8
a1 9
dp 18
l length of bolt (form B) 45 – 200
z2 12 Thread · ISO 261/262
Pitch P 3
d2 22.051
d3 20.319
Tap drill 21
Stress area As 352.5 mm² Size sheet · DIN 561 B
M30
s width across flats 36
e width across corners 39.98
k head height 21
r fillet radius 1
a1 10.5
dp 23
l length of bolt (form B) 60 – 200
z2 15 Thread · ISO 261/262
Pitch P 3.5
d2 27.727
d3 25.706
Tap drill 26.5
Stress area As 560.59 mm² Size sheet · DIN 561 B
M36
s width across flats 46
e width across corners 51.28
k head height 25
r fillet radius 1
a1 12
dp 28
l length of bolt (form B) 60 – 200
z2 18 Thread · ISO 261/262
Pitch P 4
d2 33.402
d3 31.093
Tap drill 32
Stress area As 816.72 mm² Size sheet · DIN 561 B
M42
s width across flats 55
e width across corners 61.31
k head height 30
r fillet radius 1.2
a1 13.5
dp 32
l length of bolt (form B) 80 – 260
z2 21 Thread · ISO 261/262
Pitch P 4.5
d2 39.077
d3 36.479
Tap drill 37.5
Stress area As 1120.91 mm² Size sheet · DIN 561 B
M48
s width across flats 65
e width across corners 72.61
k head height 34
r fillet radius 1.6
a1 15
dp 38
l length of bolt (form B) 90 – 300
z2 24 Thread · ISO 261/262
Pitch P 5
d2 44.752
d3 41.866
Tap drill 43
Stress area As 1473.15 mm² Size sheet · DIN 561 B
M56
s width across flats 75
e width across corners 83.91
k head height 40
r fillet radius 2
a1 16.5
dp 45
l length of bolt (form B) 100 – 300
z2 28 Thread · ISO 261/262
Pitch P 5.5
d2 52.428
d3 49.252
Tap drill 50.5
Stress area As 2030.02 mm² 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 (2) Source table repeats a row label (l form B max); the second row was not imported. Source table repeats a row label (l form B max); the second row was not imported.