ASME B1.1 Thread Dimensions — UNC Coarse Thread Chart

Unified Inch Screw Threads (UN, UNR, and UNJ Thread Forms)

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ASME B1.1 defines the standard dimensions for Unified Inch Screw Threads, including UN, UNR (rounded root), and UNJ (controlled root radius) thread forms. The table below contains data from Table 6 of ASME B1.1-2019, covering basic dimensions for the coarse-thread series (UNC, UNRC, and UNJC).

Thread sizes range from #1 (0.073") through 4", covering both numbered sizes and fractional inch sizes. All dimensions are in inches.

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Thread Dimensions Table

Use the filter below to look up thread dimensions by nominal bolt size.

Nominal Size

33 rows

Size	Major Dia. (in)	TPI	Pitch Dia. (in)	UNR Minor Ext. (in)	UNJ Minor Ext. (in)	UN Minor Int. (in)	UNJ Minor Int. (in)	Lead Angle	Minor Area (in²)	Tensile Area (in²)
#1	0.073	64	0.0629	0.0544	0.055	0.0561	0.0578	4° 32′	0.00218	0.00263
#2	0.086	56	0.0744	0.0647	0.0654	0.0667	0.0686	4° 23′	0.0031	0.0037
#3	0.099	48	0.0855	0.0742	0.075	0.0764	0.0787	4° 27′	0.00406	0.00487
#4	0.112	40	0.0958	0.0822	0.0832	0.0849	0.0876	4° 46′	0.00497	0.00604
#5	0.125	40	0.1088	0.0952	0.0962	0.0979	0.1006	4° 11′	0.00672	0.00796
#6	0.138	32	0.1177	0.1008	0.1019	0.1042	0.1076	4° 51′	0.00745	0.00908
#8	0.164	32	0.1437	0.1268	0.1279	0.1302	0.1336	3° 58′	0.012	0.014
#10	0.19	24	0.1629	0.1404	0.1419	0.1449	0.1494	4° 40′	0.0145	0.0175
#12	0.216	24	0.1889	0.1664	0.1679	0.1709	0.1754	4° 1′	0.0206	0.0242
0.25	0.25	20	0.2175	0.1905	0.1922	0.1959	0.2013	4° 12′	0.0269	0.0318
0.3125	0.3125	18	0.2764	0.2463	0.2483	0.2524	0.2584	3° 40′	0.0454	0.0524
0.375	0.375	16	0.3344	0.3006	0.3028	0.3073	0.3141	3° 25′	0.0678	0.0775
0.4375	0.4375	14	0.3911	0.3524	0.355	0.3602	0.3679	3° 20′	0.0933	0.1063
0.5	0.5	13	0.45	0.4084	0.4111	0.4167	0.4251	3° 7′	0.1257	0.1419
0.5625	0.5625	12	0.5084	0.4633	0.4663	0.4723	0.4813	2° 59′	0.162	0.182
0.625	0.625	11	0.566	0.5167	0.5201	0.5266	0.5364	2° 56′	0.202	0.226
0.75	0.75	10	0.685	0.6309	0.6345	0.6417	0.6526	2° 40′	0.302	0.334
0.875	0.875	9	0.8028	0.7427	0.7467	0.7547	0.7667	2° 31′	0.419	0.462
1	1	8	0.9188	0.8512	0.8557	0.8647	0.8782	2° 29′	0.551	0.606
1.125	1.125	7	1.0322	0.9549	0.96	0.9704	0.9858	2° 31′	0.693	0.763
1.25	1.25	7	1.1572	1.0799	1.085	1.0954	1.1108	2° 15′	0.89	0.969
1.375	1.375	6	1.2667	1.1766	1.1825	1.1946	1.2126	2° 24′	1.054	1.155
1.5	1.5	6	1.3917	1.3015	1.3075	1.3196	1.3376	2° 11′	1.294	1.405
1.75	1.75	5	1.6201	1.5118	1.5191	1.5335	1.5551	2° 15′	1.74	1.9
2	2	4.5	1.8557	1.7354	1.7434	1.7594	1.7835	2° 11′	2.3	2.5
2.25	2.25	4	2.0876	1.9523	1.9613	1.9794	2.0064	2° 11′	2.91	3.16
2.5	2.5	4	2.3376	2.2023	2.2113	2.2294	2.2564	1° 57′	3.72	4
2.75	2.75	4	2.5876	2.4523	2.4613	2.4794	2.5064	1° 46′	4.62	4.93
3	3	4	2.8376	2.7023	2.7113	2.7294	2.7564	1° 36′	5.62	5.97
3.25	3.25	4	3.0876	2.9523	2.9613	2.9794	3.0064	1° 29′	6.72	7.1
3.5	3.5	4	3.3376	3.2023	3.2113	3.2294	3.2564	1° 22′	7.92	8.33
3.75	3.75	4	3.5876	3.4523	3.4613	3.4794	3.5064	1° 16′	9.21	9.66
4	4	4	3.8376	3.7023	3.7113	3.7294	3.7564	1° 11′	10.61	11.08

Data sourced from ASME B1.1-2019, Table 6.

How to Use This Chart

Select a nominal bolt size to view its thread dimensions. The chart displays the following measurements:

Major Diameter — the basic (nominal) outside diameter of the thread
TPI — threads per inch (pitch)
Pitch Diameter — the diameter at the thread mid-height
Minor Diameter (External) — root diameter for UNR and UNJ external threads
Minor Diameter (Internal) — root diameter for UN and UNJ internal threads
Tensile Stress Area — the effective cross-sectional area used for bolt strength calculations