ANSI Internal Screw Threads Size and Tolerances Table Chart (2025)

ANSI Internal Screw Threads Size and Tolerances Table Chart

ANSI Hardware Menu
Fastener and Screw Design, Formula Calculations

  • Metric External (Fasteners) Thread Designations Sizes M1.6 - M18

  • Metric External (Fasteners) Thread and Fastener Sizes M20 - M50

  • Screw Thread Designations, Minor Diameter, Major Diameter, Pitch Diameter

ANSI/ ASME INTERNAL Screw Thread Size Chart. All units are in inches.
Unified Screw Threads per. ANSI/ASME B1.1-1989 (R2001), R2001) Nomenclature, are used. Acceptability criteria are described in ANSI/ASME B1.3M-1992 (R2001).

Note: This screw chart is not comprehensive of all available standard threads as provided by the standard.

ANSI External Screw Threads Size Chart

Screw Size Class
Thread		 Basica Minor Diameter Major
Diameter
Min. Max. Min.
0-80 2B 0.0600 0.0465 0.0514 0.0600
0-80 3B 0.0600 0.0465 0.0514 0.0600
1-64 2B 0.0730 0.0561 0.0623 0.0730
1-64 3B 0.0730 0.0561 0.0623 0.0730
1-72 2B 0.0730 0.0580 0.0635 0.0730
1-72 3B 0.0730 0.0580 0.0635 0.0730
2-56 2B 0.0860 0.0667 0.0737 0.0860
2-56 3B 0.0860 0.0667 0.0737 0.0860
2-64 2B 0.0860 0.0691 0.0753 0.0860
2-64 3B 0.0860 0.0691 0.0753 0.0860
3-48 2B 0.0990 0.0764 0.0845 0.0990
3-48 3B 0.0990 0.0764 0.0845 0.0990
3-56 2B 0.0990 0.0797 0.0865 0.0990
3-56 3B 0.0990 0.0797 0.0865 0.0990
4-40 2B 0.1120 0.0849 0.0939 0.1120
4-40 3B 0.1120 0.0849 0.0939 0.1120
4-48 2B 0.1120 0.0894 0.0968 0.1120
4-48 3B 0.1120 0.0894 0.0968 0.1120
5-40 2B 0.1250 0.0979 0.1062 0.1250
5-40 3B 0.1250 0.0979 0.1062 0.1250
5-44 2B 0.1250 0.1004 0.1079 0.1250
5-44 3B 0.1250 0.1004 0.1079 0.1250
6-32 2B 0.1380 0.1040 0.1140 0.1380
6-32 3B 0.1380 0.1040 0.1140 0.1380
6-40 2B 0.1380 0.1110 0.119 0.1380
6-40 3B 0.1380 0.1110 0.1186 0.1380
8-32 2B 0.1640 0.1300 0.139 0.1640
8-32 3B 0.1640 0.1300 0.1389 0.1640
8-36 2B 0.1640 0.1340 0.142 0.1640
8-36 3B 0.1640 0.1340 0.1416 0.1640
10-24 2B 0.1900 0.1450 0.1560 0.1900
10-24 3B 0.1900 0.1450 0.1555 0.1900
10-32 2B 0.1900 0.1560 0.1640 0.1900
10-32 3B 0.1900 0.1560 0.1641 0.1900
1/4-20 2B 0.2500 0.1960 0.2070 0.2500
1/4-20 3B 0.2500 0.1960 0.2070 0.2500
1/4-28 2B 0.2500 0.2110 0.220 0.2500
1/4-28 3B 0.2500 0.2110 0.2190 0.2500
5/16-18 2B 0.3125 0.2520 0.265 0.3125
5/16-18 3B 0.3125 0.2520 0.2630 0.3125
5/16-24 2B 0.3125 0.2670 0.277 0.3125
5/16-24 3B 0.3125 0.2670 0.2754 0.3125
3/8-16 2B 0.3750 0.3070 0.321 0.3750
3/8-16 3B 0.3750 0.3070 0.3182 0.3750
3/8-24 2B 0.3750 0.3300 0.340 0.3750
3/8-24 3B 0.3750 0.3300 0.3372 0.3750
7/16-14 2B 0.4375 0.3600 0.376 0.4375
7/16-14 3B 0.4375 0.3600 0.3717 0.4375
7/16-20 2B 0.4375 0.3830 0.395 0.4375
7/16-20 3B 0.4375 0.3830 0.3916 0.4375
1/2-13 2B 0.5000 0.4170 0.434 0.5000
1/2-13 3B 0.5000 0.4170 0.4284 0.5000
1/2-20 2B 0.5000 0.4460 0.457 0.5000
1/2-20 3B 0.5000 0.4460 0.4537 0.5000
9/16-12 2B 0.5625 0.4720 0.4900 0.5625
9/16-12 3B 0.5625 0.4720 0.4843 0.5625
9/16-14 2B 0.5625 0.4850 0.5010 0.5625
9/16-16 2B 0.5625 0.4950 0.5090 0.5625
9/16-16 3B 0.5625 0.4950 0.5040 0.5625
9/16-18 2B 0.5625 0.5020 0.5150 0.5625
9/16-18 3B 0.5625 0.5020 0.5106 0.5625
9/16-20 2B 0.5625 0.5080 0.5200 0.5625
9/16-20 3B 0.5625 0.5080 0.5162 0.5625
9/16-24 2B 0.5625 0.5170 0.5270 0.5625
9/16-24 3B 0.5625 0.5170 0.5244 0.5625
9/16-32 2B 0.5625 0.5290 0.5360 0.5625
9/16-32 3B 0.5625 0.5290 0.5344 0.5625
5/8-11 2B 0.6250 0.5270 0.546 0.6250
5/8-11 3B 0.6250 0.5270 0.5391 0.6250
5/8-18 2B 0.6250 0.5650 0.578 0.6250
5/8-18 3B 0.6250 0.5650 0.5730 0.6250
3/4-10 2B 0.7500 0.6420 0.663 0.7500
3/4-10 3B 0.7500 0.6420 0.6545 0.7500
3/4-16 2B 0.7500 0.6820 0.696 0.7500
3/4-16 3B 0.7500 0.6820 0.6908 0.7500
7/8 -9 2B 0.8750 0.7550 0.778 0.8750
7/8 -9 3B 0.8750 0.7550 0.7681 0.8750
7/8-14 2B 0.8750 0.7980 0.814 0.8750
7/8-14 3B 0.8750 0.7980 0.8068 0.8750
1 -8 2B 1.0000 0.8650 0.890 1.0000
1 -8 3B 1.0000 0.8650 0.8797 1.0000
1 -12 2B 1.0000 0.9100 0.928 1.0000
1 -12 3B 1.0000 0.9100 0.9198 1.0000
1 1/8-7 2B 1.1250 0.9700 0.998 1.1250
1 1/8-12 2B 1.1250 1.0350 1.053 1.1250
1 1/4-7 2B 1.2500 1.0950 1.123 1.2500
1 1/4-12 2B 1.2500 1.1600 1.178 1.2500
1 3/8-6 2B 1.3750 1.1950 1.225 1.3750
1 3/8-12 2B 1.3750 1.2850 1.303 1.3750
1 1/2-6 2B 1.5000 1.3200 1.350 1.5000
1 1/2-12 2B 1.5000 1.4100 1.428 1.5000
1 3/4-5 2B 1.7500 1.5340 1.568 1.7500
2 -6 2B 2.0000 1.820 1.850 2.0000
Screw Size Class
Thread		 Pitch Diameter
Min. Max.
0-80 2B 0.0519 0.0542
0-80 3B 0.0519 0.0536
1-64 2B 0.0629 0.0655
1-64 3B 0.0629 0.0648
1-72 2B 0.0640 0.0665
1-72 3B 0.0640 0.0659
2-56 2B 0.0744 0.0772
2-56 3B 0.0744 0.0765
2-64 2B 0.0759 0.0786
2-64 3B 0.0759 0.0779
3-48 2B 0.0855 0.0885
3-48 3B 0.0855 0.0877
3-56 2B 0.0874 0.0902
3-56 3B 0.0874 0.0895
4-40 2B 0.0958 0.0991
4-40 3B 0.0958 0.0982
4-48 2B 0.0985 0.1016
4-48 3B 0.0985 0.1008
5-40 2B 0.1088 0.1121
5-40 3B 0.1088 0.1113
5-44 2B 0.1102 0.1134
5-44 3B 0.1102 0.1126
6-32 2B 0.1177 0.1214
6-32 3B 0.1177 0.1204
6-40 2B 0.1218 0.1252
6-40 3B 0.1218 0.1243
8-32 2B 0.1437 0.1475
8-32 3B 0.1437 0.1465
8-36 2B 0.1460 0.1496
8-36 3B 0.1460 0.1487
10-24 2B 0.1629 0.1672
10-24 3B 0.1629 0.1661
10-32 2B 0.1697 0.1736
10-32 3B 0.1697 0.1726
1/4-20 2B 0.2175 0.2248
1/4-20 3B 0.2175 0.2211
1/4-28 2B 0.2268 0.2311
1/4-28 3B 0.2268 0.2300
5/16-18 2B 0.2764 0.2817
5/16-18 3B 0.2764 0.2803
5/16-24 2B 0.2854 0.2902
5/16-24 3B 0.2854 0.2890
3/8-16 2B 0.3344 0.3401
3/8-16 3B 0.3344 0.3387
3/8-24 2B 0.3479 0.3528
3/8-24 3B 0.3479 0.3516
7/16-14 2B 0.3911 0.3972
7/16-14 3B 0.3911 0.3957
7/16-20 2B 0.4050 0.4104
7/16-20 3B 0.4050 0.4091
1/2-13 2B 0.4500 0.4565
1/2-13 3B 0.4500 0.4548
1/2-20 2B 0.4675 0.4731
1/2-20 3B 0.4675 0.4717
9/16-12 2B 0.5084 0.5152
9/16-12 3B 0.5084 0.5135
9/16-14 2B 0.5161 0.5226
9/16-16 2B 0.5219 0.5280
9/16-16 3B 0.5219 0.5265
9/16-18 2B 0.5264 0.5323
9/16-18 3B 0.5264 0.5308
9/16-20 2B 0.5300 0.5355
9/16-20 3B 0.5300 0.5341
9/16-24 2B 0.5354 0.5404
9/16-24 3B 0.5354 0.5392
9/16-32 2B 0.5422 0.5467
9/16-32 3B 0.5422 0.5456
5/8-11 2B 0.5660 0.5732
5/8-11 3B 0.5660 0.5714
5/8-18 2B 0.5889 0.5949
5/8-18 3B 0.5889 0.5934
3/4-10 2B 0.6850 0.6927
3/4-10 3B 0.6850 0.6907
3/4-16 2B 0.7094 0.7159
3/4-16 3B 0.7094 0.7143
7/8 -9 2B 0.8028 0.8110
7/8 -9 3B 0.8028 0.8089
7/8-14 2B 0.8286 0.8356
7/8-14 3B 0.8286 0.8339
1 -8 2B 0.9188 0.9276
1 -8 3B 0.9188 0.9254
1 -12 2B 0.9459 0.9535
1 -12 3B 0.9459 0.9516
1 1/8-7 2B 1.0322 1.0416
1 1/8-12 2B 1.0709 1.0787
1 1/4-7 2B 1.1572 1.1668
1 1/4-12 2B 1.1959 1.2039
1 3/8-6 2B 1.2667 1.2771
1 3/8-12 2B 1.3209 1.3291
1 1/2-6 2B 1.3917 1.4022
1 1/2-12 2B 1.4459 1.4542
1 3/4-5 2B 1.6201 1.6317
2 -6 2B 1.8917 1.9028

a. Basic = Nominal

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ANSI Internal Screw Threads Size and Tolerances Table Chart (2025)
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