Dimensions mm · values as the standard states them Size P dk actual dk theoretical b r t hexalobular A hexalobular kc recess_no hexalobular M2 0.4 3.8
3.5 – 3.8
≤ 4.4
≥ 25
≤ 0.5
0.51 – 0.64
(1.75)
1.2
≤ 1.2
6
M2.5 0.45 4.7
4.4 – 4.7
≤ 5.5
≥ 25
≤ 0.6
0.66 – 0.79
(2.4)
1.5
≤ 1.5
8
M3 0.5 5.5
5.2 – 5.5
≤ 6.3
≥ 25
≤ 0.8
0.7 – 0.83
(2.8)
1.65
≤ 1.65
10
M3.5 0.6 7.3
6.94 – 7.3
≤ 8.2
≥ 38
≤ 0.9
1.16 – 1.32
(3.35)
2.35
≤ 2.35
15
M4 0.7 8.4
8.04 – 8.4
≤ 9.4
≥ 38
≤ 1
1.14 – 1.53
(3.95)
2.7
≤ 2.7
20
M5 0.8 9.3
8.94 – 9.3
≤ 10.4
≥ 38
≤ 1.3
1.12 – 1.51
(4.5)
2.7
≤ 2.7
25
M6 1 11.3
10.87 – 11.3
≤ 12.6
≥ 38
≤ 1.5
1.39 – 1.78
(5.6)
3.3
≤ 3.3
30
M8 1.25 15.8
15.37 – 15.8
≤ 17.3
≥ 38
≤ 2
2.15 – 2.54
(7.95)
4.65
≤ 4.65
45
M10 1.5 18.3
17.78 – 18.3
≤ 20
≥ 38
≤ 2.5
2.41 – 2.8
(8.98)
5
≤ 5
50
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 3 2.8 – 3.2
4 3.76 – 4.24
5 4.76 – 5.25
6 5.76 – 6.24
8 7.71 – 8.29
10 9.71 – 10.29
12 11.65 – 12.35
14 13.65 – 14.35
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 54.05 – 55.95
60 59.05 – 60.95
Size sheet · ISO 14581
M2
dk head diameter (actual) 3.8
dk head diameter (theoretical) ≤ 4.4
b thread length ≥ 25
r fillet radius ≤ 0.5
t groove depth (hexalobular) 0.51 – 0.64
A groove (hexalobular) (1.75)
kc 1.2
recess_no drive size (hexalobular) 6 Thread · ISO 261/262
Pitch P 0.4
d2 1.74
d3 1.509
Tap drill 1.6
Stress area As 2.07 mm² Standard lengths
3 · 4 · 5 · 6 · 8 · 10 · 12 · 14 · 16 · 20
Size sheet · ISO 14581
M2.5
dk head diameter (actual) 4.7
dk head diameter (theoretical) ≤ 5.5
b thread length ≥ 25
r fillet radius ≤ 0.6
t groove depth (hexalobular) 0.66 – 0.79
A groove (hexalobular) (2.4)
kc 1.5
recess_no drive size (hexalobular) 8 Thread · ISO 261/262
Pitch P 0.45
d2 2.208
d3 1.948
Tap drill 2.05
Stress area As 3.39 mm² Standard lengths
3 · 4 · 5 · 6 · 8 · 10 · 12 · 14 · 16 · 20 · 25
Size sheet · ISO 14581
M3
dk head diameter (actual) 5.5
dk head diameter (theoretical) ≤ 6.3
b thread length ≥ 25
r fillet radius ≤ 0.8
t groove depth (hexalobular) 0.7 – 0.83
A groove (hexalobular) (2.8)
kc 1.65
recess_no drive size (hexalobular) 10 Thread · ISO 261/262
Pitch P 0.5
d2 2.675
d3 2.387
Tap drill 2.5
Stress area As 5.03 mm² Standard lengths
4 · 5 · 6 · 8 · 10 · 12 · 14 · 16 · 20 · 25 · 30
Size sheet · ISO 14581
M3.5
dk head diameter (actual) 7.3
dk head diameter (theoretical) ≤ 8.2
b thread length ≥ 38
r fillet radius ≤ 0.9
t groove depth (hexalobular) 1.16 – 1.32
A groove (hexalobular) (3.35)
kc 2.35
recess_no drive size (hexalobular) 15 Thread · ISO 261/262
Pitch P 0.6
d2 3.11
d3 2.764
Tap drill 2.9
Stress area As 6.78 mm² Standard lengths
5 · 6 · 8 · 10 · 12 · 14 · 16 · 20 · 25 · 30 · 35
Size sheet · ISO 14581
M4
dk head diameter (actual) 8.4
dk head diameter (theoretical) ≤ 9.4
b thread length ≥ 38
r fillet radius ≤ 1
t groove depth (hexalobular) 1.14 – 1.53
A groove (hexalobular) (3.95)
kc 2.7
recess_no drive size (hexalobular) 20 Thread · ISO 261/262
Pitch P 0.7
d2 3.545
d3 3.141
Tap drill 3.3
Stress area As 8.78 mm² Standard lengths
5 · 6 · 8 · 10 · 12 · 14 · 16 · 20 · 25 · 30 · 35 · 40
Size sheet · ISO 14581
M5
dk head diameter (actual) 9.3
dk head diameter (theoretical) ≤ 10.4
b thread length ≥ 38
r fillet radius ≤ 1.3
t groove depth (hexalobular) 1.12 – 1.51
A groove (hexalobular) (4.5)
kc 2.7
recess_no drive size (hexalobular) 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
6 · 8 · 10 · 12 · 14 · 16 · 20 · 25 · 30 · 35 · 40 · 45 · 50
Size sheet · ISO 14581
M6
dk head diameter (actual) 11.3
dk head diameter (theoretical) ≤ 12.6
b thread length ≥ 38
r fillet radius ≤ 1.5
t groove depth (hexalobular) 1.39 – 1.78
A groove (hexalobular) (5.6)
kc 3.3
recess_no drive size (hexalobular) 30 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 · 12 · 14 · 16 · 20 · 25 · 30 · 35 · 40 · 45 · 50 · 55 · 60
Size sheet · ISO 14581
M8
dk head diameter (actual) 15.8
dk head diameter (theoretical) ≤ 17.3
b thread length ≥ 38
r fillet radius ≤ 2
t groove depth (hexalobular) 2.15 – 2.54
A groove (hexalobular) (7.95)
kc 4.65
recess_no drive size (hexalobular) 45 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 · 12 · 14 · 16 · 20 · 25 · 30 · 35 · 40 · 45 · 50 · 55 · 60
Size sheet · ISO 14581
M10
dk head diameter (actual) 18.3
dk head diameter (theoretical) ≤ 20
b thread length ≥ 38
r fillet radius ≤ 2.5
t groove depth (hexalobular) 2.41 – 2.8
A groove (hexalobular) (8.98)
kc 5
recess_no drive size (hexalobular) 50 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
12 · 14 · 16 · 20 · 25 · 30 · 35 · 40 · 45 · 50 · 55 · 60
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.