Metric Bolt Sizes

Metric bolt sizes are written as M followed by a number (e.g., M10 or M32). The number represents the major diameter of the bolt in millimetres. The major diameter is the largest outside diameter of the bolt thread.

Metric Bolt Sizes Table

Bolt Size Major Diameter (mm) Minor Diameter (mm) Pitch (mm) Pitch Diameter (mm) Tapping Drill Size (mm) Clearance Hole Size (mm)
M1 1 0.729 0.25 0.838 0.75 1.3
M1.1 1.1 0.829 0.25 0.938 0.85 1.4
M1.2 1.2 0.929 0.25 1.038 0.95 1.5
M1.4 1.4 1.075 0.3 1.205 1.1 1.8
M1.6 1.6 1.221 0.35 1.373 1.25 2
M1.8 1.8 1.421 0.35 1.573 1.45 2.3
M2 2 1.567 0.4 1.74 1.6 2.6
M2.2 2.2 1.713 0.45 1.908 1.75 2.9
M2.5 2.5 2.013 0.45 2.208 2.05 3.1
M3 3 2.459 0.5 2.675 2.5 3.6
M3.5 3.5 2.85 0.6 3.11 2.9 4.2
M4 4 3.242 0.7 3.545 3.3 4.8
M4.5 4.5 3.688 0.75 4.013 3.8 5.3
M5 5 4.134 0.8 4.48 4.2 5.8
M6 6 4.917 1 5.35 5 7
M7 7 5.917 1 6.35 6 8
M8 8 6.647 1.25 7.188 6.8 10
M9 9 7.647 1.25 8.188 7.8 11
M10 10 8.376 1.5 9.026 8.5 12
M11 11 9.376 1.5 10.026 9.5 13.5
M12 12 10.106 1.75 10.863 10.2 15
M14 14 11.835 2 12.701 12 17
M16 16 13.835 2 14.701 14 19
M18 18 15.394 2.5 16.376 15.5 22
M20 20 17.294 2.5 18.376 17.5 24
M22 22 19.294 2.5 20.376 19.5 26
M24 24 20.752 3 22.051 21 28
M27 27 23.752 3 25.051 24 33
M30 30 26.211 3.5 27.727 26.5 35
M33 33 29.211 3.5 30.727 29.5 38
M36 36 31.67 4 33.402 32 41
M39 39 34.67 4 36.402 35 44
M42 42 37.129 4.5 39.077 37.5 47
M45 45 40.129 4.5 42.077 40.5 50
M48 48 42.857 5 44.752 43 53
M52 52 46.587 5 48.752 47 57
M56 56 50.046 5.5 52.428 50.5 61
M60 60 54.046 5.5 56.428 54.5 65
M64 64 57.505 6 60.103 58 69
M68 68 61.505 6 64.103 62 73
M72 72 65.505 6 68.103 66 77
M76 76 69.505 6 72.103 70 81
M80 80 73.505 6 76.103 74 85
M85 85 78.046 6 81.103 79 90
M90 90 83.046 6 86.103 84 95
M95 95 88.046 6 91.103 89 100
M100 100 93.046 6 96.103 94 105

Metric Bolt Sizes Table - Imperial

Bolt Size Major Diameter (inches) Minor Diameter (inches) Pitch (inches) Pitch Diameter (inches) Tapping Drill Size (inches) Clearance Hole Size (inches)
M1 0.039 0.029 0.010 0.033 0.030 0.051
M1.1 0.043 0.033 0.010 0.037 0.033 0.055
M1.2 0.047 0.037 0.010 0.041 0.037 0.059
M1.4 0.055 0.042 0.012 0.047 0.043 0.071
M1.6 0.063 0.048 0.014 0.054 0.049 0.079
M1.8 0.071 0.056 0.014 0.062 0.057 0.091
M2 0.079 0.062 0.016 0.069 0.063 0.102
M2.2 0.087 0.067 0.018 0.075 0.069 0.114
M2.5 0.098 0.079 0.018 0.087 0.081 0.122
M3 0.118 0.097 0.020 0.105 0.098 0.142
M3.5 0.138 0.112 0.024 0.122 0.114 0.165
M4 0.157 0.128 0.028 0.140 0.130 0.189
M4.5 0.177 0.145 0.030 0.158 0.150 0.209
M5 0.197 0.163 0.031 0.176 0.165 0.228
M6 0.236 0.194 0.039 0.211 0.197 0.276
M7 0.276 0.233 0.039 0.250 0.236 0.315
M8 0.315 0.262 0.049 0.283 0.268 0.394
M9 0.354 0.301 0.049 0.322 0.307 0.433
M10 0.394 0.330 0.059 0.355 0.335 0.472
M11 0.433 0.369 0.059 0.395 0.374 0.531
M12 0.472 0.398 0.069 0.428 0.402 0.591
M14 0.551 0.466 0.079 0.500 0.472 0.669
M16 0.630 0.545 0.079 0.579 0.551 0.748
M18 0.709 0.606 0.098 0.645 0.610 0.866
M20 0.787 0.681 0.098 0.723 0.689 0.945
M22 0.866 0.760 0.098 0.802 0.768 1.024
M24 0.945 0.817 0.118 0.868 0.827 1.102
M27 1.063 0.935 0.118 0.986 0.945 1.299
M30 1.181 1.032 0.138 1.092 1.043 1.378
M33 1.299 1.150 0.138 1.210 1.161 1.496
M36 1.417 1.247 0.157 1.315 1.260 1.614
M39 1.535 1.365 0.157 1.433 1.378 1.732
M42 1.654 1.462 0.177 1.538 1.476 1.850
M45 1.772 1.580 0.177 1.657 1.594 1.969
M48 1.890 1.687 0.197 1.762 1.693 2.087
M52 2.047 1.834 0.197 1.919 1.850 2.244
M56 2.205 1.970 0.217 2.064 1.988 2.402
M60 2.362 2.128 0.217 2.222 2.146 2.559
M64 2.520 2.264 0.236 2.366 2.283 2.717
M68 2.677 2.421 0.236 2.524 2.441 2.874
M72 2.835 2.579 0.236 2.681 2.598 3.031
M76 2.992 2.736 0.236 2.839 2.756 3.189
M80 3.150 2.894 0.236 2.996 2.913 3.346
M85 3.346 3.073 0.236 3.193 3.110 3.543
M90 3.543 3.270 0.236 3.390 3.307 3.740
M95 3.740 3.466 0.236 3.587 3.504 3.937
M100 3.937 3.663 0.236 3.784 3.701 4.134

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