Technical Information

ISO General Purpose Metric Screw Threads

A screw thread in conformity with this International Standard is designated by the letter M followed by the values of the nominal diameter and of the pitch expressed in millimeters separated by the sign x.

Example : M 6 x 0.75 (Fine pitch 0.75)

The absence of the indication of pitch means that the coarse pitch is specified.

Example : M 6 (Coarse pitch 1.0)

The words "coarse" and "fine" are given in order to conform to usage. No concept of quality however, is associated with these words. "Coarse" pitches are the largest metric pitches used. For the diameter selected, choose one of the pitches shown on the corresponding line.

Diameter / Pitch Combinations

Nominal Diameters Pitches
1st Choice 2nd Choice 3rd Choice Coarse (mm) Fine (mm)
M 1     0.25 0.2
  M 1.1   0.25 0.2
M 1.2     0.25 0.2
  M 1.4   0.3 0.2
M 1.6     0.35 0.2
  M 1.8   0.35 0.2
M 2     0.4 0.25
  M 2.2   0.45 0.25
M 2.5     0.45 0.35
M 3     0.5 0.35
  M 3.5   0.6 0.35
M 4     0.7 0.5
  M 4.5   0.75 0.5
M 5     0.8 0.5
    M 5.5   0.5
M6     1.0 0.75
    M 7 1 0.75
M 8     1.25 1, 0.75
    M 9 1.25 1, 0.75
M 10     1.5 1.25, 1, 0.75
    M 11 1.5 1, 0.75
M 12     1.75 1.5, 1.25, 1
  M14   2 1.5, 1.25, 1
    M 15   1.5, 1
M 16     2 1.5, 1
    M 17   1.5, 1
  M 18   2.5 2, 1.5, 1
M 20     2.5 2, 1.5, 1
  M 22   2.5 2, 1.5, 1
M 24     3 2, 1.5, 1
    M 25   2, 1.5, 1
    M 26   1.5
  M 27   3 2, 1.5, 1
    M 28   2, 1.5, 1
M 30     3.5 3, 2, 1.5, 1
    M 32   2, 1.5
  M 33   3.5 3, 2, 1.5
    M 35   1.5
M 36     4 3, 2, 1.5
    M 38   1.5
  M 39   4 3, 2, 1.5
    M 40   3, 2, 1.5
M 42     4.5 4, 3, 2, 1.5
  M 45   4, 5 4, 3, 2, 1.5
M 48     5 4, 3, 2, 1.5
    M 50   3, 2, 1.5
  M 52   5 4, 3, 2, 1.5
    M 55   4, 3, 2, 1.5
M 56     5.5 4, 3, 2, 1.5
    M 58   4, 3, 2, 1.5
  M 60   5.5 4, 3, 2, 1.5
    M 62   4, 3, 2, 1.5
M 64     6 4, 3, 2, 1.5
    M 65   4, 3, 2, 1.5
  M 68   6 4, 3, 2, 1.5
    M 70   6, 4, 3, 2, 1.5
M 72       6, 4, 3, 2, 1.5
    M 75   4, 3, 2, 1.5
  M 76     6, 4, 3, 2, 1.5
    M 78   2
M 80       6, 4, 3, 2, 1.5
    M 82   2
  M 85     6, 4, 3, 2
M 90       6, 4, 3, 2
  M 95     6, 4, 3, 2
M 100       6, 4, 3, 2
  M 105     6, 4, 3, 2
M 110       6, 4, 3, 2
  M 115     6, 4, 3, 2
  M 120     6, 4, 3, 2
M 125       6, 4, 3, 2
  M 130     6, 4, 3, 2
    M 135   6, 4, 3, 2
M 140       6, 4, 3, 2
    M 145   6, 4, 3, 2
  M 150     6, 4, 3, 2
    M 155   6, 4, 3
M 160       6, 4, 3
    M 165   6, 4, 3
  M 170     6, 4, 3
    M 175   6, 4, 3
M 180       6, 4, 3
    M 185   6, 4, 3
  M 190     6, 4, 3
    M 195   6, 4, 3
M 200       6, 4, 3
    M 205   6, 4, 3
  M 210     6, 4, 3
    M215   6, 4, 3
M 220       6, 4, 3
    M 225   6, 4, 3
    M 230   6, 4, 3
    M 235   6, 4, 3
  M 240     6, 4, 3
    M 245   6, 4, 3
M 250       6, 4, 3
    M 255   6, 4
  M 260     6, 4
    M 265   6, 4
    M 270   6, 4
    M 275   6, 4
M 280       6, 4
    M 285   6, 4
    M 290   6, 4
    M 295   6, 4
  M 300     6, 4

Limits of Sizes for Bolt & Nut Threads

Reference No.: ISO 965/1-1980, ISO 965/2-1980

Bolt Threads (Coarse)

MAJOR DIAMETER PITCH DIAMETER Root Radius (min. 1)
max. min. max. min.  
1,000 0,933 0,838 0,785 0,031
1,100 1,033 0,938 0,885 0,031
1,200 1,133 1,038 0,985 0,031
1,400 1,325 1,205 1,149 0,038
1,581 1,496 1,354 1,291 0,044
1,781 1,696 1,554 1,491 0,044
1,981 1,886 1,721 1,654 0,050
2,180 2,080 1,888 1,817 0,056
2,480 2,380 2,188 2,117 0,056
2,980 2,874 2,655 2,580 0,063
3,479 3,354 3,089 3,004 0,075
3,978 3,838 3,523 3,433 0,088
4,478 4,338 3,991 3,901 0,094
4,976 4,826 4,456 4,361 0,100
5,974 5,794 5,324 5,212 0,125
6,974 6,794 6,324 6,212 0,125
7,972 7,760 7,160 7,042 0,156
9,968 9,732 8,994 8,862 0,188
11,966 11,701 10,829 10,679 0,219
13,962 13,682 12,663 12,503 0,250
15,962 15,682 14,663 14,503 0,250
17,958 17,623 16,334 16,164 0,313
19,958 19,623 18,334 18,164 0,313
21,958 21,623 20,334 20,164 0,313
23,952 23,577 22,003 21,803 0,375
26,952 26,577 25,003 24,803 0,375
29,947 29,522 27,674 27,462 0,438
32,947 32,522 30,674 30,462 0,438
35,940 35,465 33,342 33,118 0,500
38,940 38,465 36,342 36,118 0,500

BOLT THREADS (FINE)

MAJOR DIAMETER PITCH DIAMETER Root Radius (min. 1)
max. min. max. min.  
7,974 7,794 7,324 7,212 0,125
9,972 9,760 9,160 9,042 0,156
11,972 11,760 11,160 11,028 0,156
13,968 13,732 12,994 12,854 0,188
15,968 15,732 14,994 14,854 0,188
17,968 17,732 16,994 16,854 0,188
19,968 19,732 18,994 18,854 0,188
21,968 21,732 20,994 20,854 0,188
23,962 23,682 22,663 22,493 0,250
26,962 26,682 25,663 25,493 0,250
29,962 29,682 28,663 28,493 0,250
32,962 32,682 31,663 31,493 0,250
35,952 35,577 34,003 33,803 0,375
38,952 38,577 37,003 36,803 0,375

NUT THREADS (COARSE)

PITCH DIAMETER MINOR DIAMETER
max. min. max. min.
0,894 0,838 0,785 0,729
0,994 0,938 0,885 0,729
1,094 1,038 0,985 0,929
1,265 1,205 1,142 1,075
1,458 1,373 1,321 1,221
1,658 1,573 1,521 1,421
1,830 1,740 1,679 1,567
2,003 1,908 1,838 1,713
2,303 2,208 2,138 2,013
2,775 2,675 2,599 2,459
3,222 3,110 3,010 2,850
3,663 3,545 3,422 3,242
4,131 4,013 3,878 3,688
4,605 4,480 4,334 4,134
5,500 5,350 5,153 4,917
6,500 6,350 6,153 5,917
7,348 7,188 6,912 6,647
9,206 9,026 8,676 8,376
11,063 10,863 10,441 10,106
12,913 12,701 12,210 11,835
14,913 14,701 14,210 13,835
16,600 16,376 15,744 15,294
18,600 18,376 17,744 17,294
20,600 20,376 19,744 19,294
22,316 22,051 21,252 20,752
25,316 25,051 24,252 23,752
28,007 27,727 26,771 26,211
31,007 30,727 29,771 29,211
33,702 33,402 32,270 31,670
36,702 36,402 35,270 34,670

NUT THREADS (FINE)

PITCH DIAMETER MINOR DIAMETER
max. min. max. min.
7,500 7,350 7,153 6,917
9,348 9,188 8,912 8,647
11,368 11,188 10,912 10,647
13,216 13,026 12,676 12,376
15,216 15,026 14,676 14,376
17,216 17,026 16,676 16,376
19,216 19,026 18,676 18,376
21,216 21,026 20,676 20,376
22,925 22,701 22,210 21,835
25,925 25,701 25,210 24,835
28,925 28,701 28,210 27,835
31,925 31,701 31,210 30,835
34,316 34,051 33,252 32,752
37,316 37,051 36,252 35,752

(COARSE)

Thread Size in mm Length of Thread engagement
  over up to and incl.
M 1 0,6 1,7
M 1, 1 0,6 1,7
M 1, 2 0, 6 1, 7
M 1, 4 0, 7 2
M 1, 6 0, 8 2, 6
M 1, 8 0, 8 2, 6
M 2 1 3
M 2, 2 1, 3 3, 8
M 2, 5 1, 3 3, 8
M 3 1, 5 4, 5
M 3, 5 1, 7 5
M 4 2 6
M 4, 5 2, 2 6, 7
M 5 2, 5 7, 5
M 6 3 9
M 7 3 3
M 8 4 12
M 10 5 15
M 12 6 18
M 14 8 24
M 16 8 24
M 18 10 30
M 20 10 30
M 22 10 30
M 24 12 36
M 27 12 36
M 30 15 45
M 33 15 45
M 36 18 53
M 39 18 53

(FINE)

Thread Size in mm Length of Thread engagement
  over up to and incl.
M 8 x 1 3 9
M 10 x 1,25 4 12
M 12 x 1,25 4, 5 13
M 14 x 1,5 5, 6 16
M 16 x 1,5 5, 6 16
M 18 x 1,5 5, 6 16
M 20 x 1,5 5, 6 16
M 22 x 1,5 5, 6 16
M 24 x 2 8, 5 25
M 27 x 2 8, 5 25
M 30 x 2 8, 5 25
M 33 x 2 8, 5 25
M 36 x 3 12 36
M 39 x 3 12 36

Screw Thread Conversion Table

MAJOR DIAMETER

NOMINAL DIAMETER (mm) MAJOR DIAMETER
  mm INCH
M 1 1 .0393
M 1.1 1.1 .0433
M 1.2 1.2 .0472
M 1.4 1.4 .0551
M 1.6 1.6 .0629
M 1.8 1.8 .0708
M 2 2 .0787
M 2.2 2.2 .0866
M 2.3 2.3 .0905
M 2.5 2.5 .0984
M 2.6 2.6 .1023
M 3 3 .1181
M 3.5 3.5 .1378
M 4 4 .1574
M 4.5 4.5 .1771
M 5 5 .1968
M 6 6 .2362
M 7 7 .2755
M 8 8 .3149
M 10 10 .3937
M 12 12 .4724
M 14 14 .5511
M 16 16 .6299
M 18 18 .7086
M 20 20 .874
M 22 22 .8661
M 24 24 .9448
M 27 27 1.0629
M 30 30 1.181
M 33 33 1.299
M 36 36 1.417
M 39 39 1.535
M 42 42 1.654
M 45 45 1.772
M 48 48 1.890
M 52 52 2.047
M 56 56 2.205
M 60 60 2.362
M 64 64 2.520
M 68 68 2.677
M 72 72 2.835
M 76 76 2.992
M 80 80 3.150
M 85 85 3.346
M 90 90 3.543
M 95 95 3.740
M 100 100 3.937
M 105 105 4.134
M 110 110 4.331
M 115 115 4.538
M 120 120 4.724
M 125 125 4.921
M 130 130 5.118
M 135 135 5.315
M 140 140 5.512
M 145 145 5.709
M 150 150 5.906

THREAD PITCH

PITCH (mm) Approx. Threads per Inch
0.08 317.5
0.09 282.25
0.1 254
0.125 203.25
0.15 169.25
0.175 145.25
0.2 127
0.225 113
0.25 101.5
0.3 84.75
0.35 72.5
0.4 63.5
0.45 56.5
0.5 50.75
0.6 42.25
0.7 36.25
0.75 33.75
0.8 31.75
0.9 25.25
1 25.5
1.25 20.25
1.5 17
1.75 14.25
2 12.75
2.5 10.25
3 8.5
3.5 7.25
4 6.25
5 5
5.5 4.5
6 4.25

US / Metric Conversion Equivalents

To convert length to mm multiply inches by 25.4

To convert length to inches multiply mm by .039370

LENGTH CONVERSION

U.S. TO METRIC METRIC TO U.S.
1 inch 25.400 millimetres 1 millimetre : .03937 inches
1 inch 2.540 centimetres 1 centimetre : .39370 inches
1 foot 30.480 centimetres 1 metre : 3.2808 feet
1 yard 0.9144 metres 1 metre : 1.0936 yards
1 mile 1,609 kilometres 1 centimetre : .62137 miles

AREA CONVERSION

U.S. TO METRIC METRIC TO U.S.
1 sq. inch 6.4516 sq. centimetres 1 sq. centimetre : .1550 sq. inches
1 sq. foot .0929 sq. metres 1 sq. metre : 10.764 sq. feet
1 sq. mile 2.5889 sq. kilometres 1 sq. kilometre : .38614 sq. miles

AREA

Sq. Inch centimetre square centimetre square Sq. Inch
1 6.45 1 .1550
2 12.90 2 .310
3 2.5889 sq. kilometres 3 .456
4 25.81 4 .620
5 32.26 5 .775
Sq. Feet metre square metre square Sq. Feet
1 .093 1 10.76
2 .186 2 21.53
3 .279 3 32.29
4 .372 4 43.06
5 .465 5 53.82

VOLUME

Cu. Inch centimetre cube centimetre cube Cu. Inch
1 16.39 1 .061
2 32.77 2 .122
3 49.16 3 .183
4 65.55 4 .244
5 81.94 5 .305
Cu. Feet metre cube metre cube Cu. Feet
1 .028 1 .061
2 .057 2 70.63
3 .085 3 105.94
4 .113 4 141.26
5 .142 5 176.57

CAPACITY

Quart Liter Liter Quart
1 1.101 1 .908
2 2.202 2 1.816
3 3.303 3 2.724
4 4.404 4 3.632
5 5.505 5 4.540
US Gallon Liter Liter US Gallon
1 3.79 1 .26
2 7.57 2 .53
3 11.36 3 .79
4 15.14 4 1.06
5 18.93 5 1.32

MASS (WEIGHT)

Lb. kg kg Lb.
1 .45 1 2.20
2 .91 2 4.41
3 1.36 3 6.61
4 1.81 4 8.82
5 2.27 5 11.02
Oz. gr gr Oz.
1 28.35 1 .035
2 56.70 2 .071
3 85.05 3 .106
4 113.40 4 .141
5 141.75 5 .176

PRESSURE

Lb. / Sq. In kg / centimetre square kg / centimetre square Lb. / Sq. In
1 .070 1 14.22
2 .141 2 28.45
3 .211 3 42.67
4 .281 4 56.89
5 .352 5 71.12
Lb. / Sq. Ft. kg / metre square kg / metre square Lb. / Sq. Ft.
1 4.88 1 .20
2 9.76 2 .41
3 14.65 3 .61
4 19.53 4 .82
5 24.41 5 1.02