ANSI Internal Screw Threads Size and Tolerances Table Chart (2024)

ANSI Internal Screw Threads Size and Tolerances Table Chart

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Fastener and Screw Design, Formula Calculations

Metric External (Fasteners) Thread Designations Sizes M1.6 - M18
Metric External (Fasteners) Thread and Fastener Sizes M20 - M50
See Also
Deck Screw Size Chart: Sizes and How to Pick the Right Type What Size Drill Bit for #8 & #10 Screw? Pilot Hole Size Chart Difference between M5 and 10-32 UNF?Wood Screw Sizes. Chart With Screw Number and Diameter
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	Basic^a	Minor Diameter		Major Diameter
Screw Size	Class Thread	Basic^a	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
Screw Size	Class Thread	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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