Thread Identification Chart (American Standard)

Basic Major Diameter
Basic Major Diameter		Nom Dia.	Threads Per Inch
Inch	mm		UNC	UNF	UNEF	UNM
.0118	0.30
.0118	0.30	0.30				318
.0138	0.35	0.35				282
.0146	0.37
.0157	0.40	0.40				254
.0165	0.42
.0177	0.45	0.45				254
.0189	0.48
.0197	0.50	0.50				203
.0209	0.53			160
.0213	0.54
.0217	0.55	0.55				203
.0236	0.60	0.60				169
.0244	0.62
.0276	0.70	0.70				145
.0311	0.79
.0315	0.80	0.80				127
.0340	0.86			120
.0354	0.90	0.90				113
.0394	1.00	1.00				102
.0433	1.10	1.10				102
.0470	1.19			90	96
.0472	1.20	1.20
.0512	1.30
.0551	1.40	1.40				85
.0591	1.50
.0600	1.52			80
.0629	1.60
.0669	1.70
.0709	1.80
.0730	1.85	#1	64	72
.0748	1.90
.0787	2.00
.0860	2.18	#2	56	64
.0866	2.20
.0906	2.30
.0984	2.50
.0990	2.51	#3	48	56
.1024	2.60
.1102	2.80
.1120	2.84	#4	40	48
.1181	3.00
.1250	3.18	#5	40	44
.1260	3.20
.1380	3.50	#6	32	40
.1417	3.60
.1575	4.00
.1614	4.10
.1640	4.17	#8	32	36
.1772	4.50
.1850	4.70
.1875	4.76
.1900	4.83	#10	24	32
.1969	5.00
.2087	5.30
.2160	5.49	#12	24	28	32
.2165	5.50
.2188	5.56
.2362	6.00
.2500	6.35	1/4	20	28	32
.2756	7.00
.2812	7.14
.3125	7.94	5/16	18	24	32
.3125	7.94	1/16				27
.3150	8.00
.3543	9.00
.3750	9.53	3/8	16	24	32
.3830	9.73
.3937	10.00
.4050	10.29	1/8				27
.4331	11.00
.4375	11.11	7/16	14	20	28
.4724	12.00
.5000	12.70	1/2	13	20	28
.5180	13.16
.5400	13.72	1/4				18
.5512	14.00
.5625	14.29	9/16	12	18	24
.6250	15.88	5/8	11	18	24
.6299	16.00
.6560	16.66
.6750	17.15	3/8				18
.6875	17.46	11/16			24
.7087	18.00
.7500	19.05	3/4	10	16	20
.7874	20.00
.8125	20.64	13/16			20
.8250	20.96
.8400	21.34	1/2				14
.8661	22.00
.8750	22.23	7/8	9	14	20
.9020	22.91
.9375	23.81	15/16			20
.9449	24.00
1.0000	25.40	1	8	14	20
1.0236	26.00
1.0410	26.44
1.0500	26.67	3/4				14
1.0625	26.99	1 1/16			18
1.0630	27.00
1.1250	28.58	1 1/8	7	12	18
1.1811	30.00
1.1875	30.16	1 3/16			18
1.1890	30.20
1.2500	31.75	1 1/4	7	12	18
1.2598	32.00
1.2992	33.00
1.3090	33.25
1.3125	33.34	1 5/16			18
1.3150	33.40	1				11 1/2
1.3750	34.93	1 3/8	6	12	18
1.3780	35.00
1.4173	36.00
1.4375	36.51	1 7/16			18
1.4920	37.90
1.4961	38.00
1.5000	38.10	1 1/2	6	12	18
1.5354	39.00
1.5625	39.69	1 9/16			18
1.5748	40.00
1.6250	41.28	1 5/8			18
1.6500	41.91
1.6535	42.00
1.6600	42.16	1 1/4				11 1/2
1.6875	42.86	1 11/16			18
1.7450	44.32

UNC-Unified National Course
UNF-Unified National Fine
UNEF-Unified National Extra Fine
UNM-Unified National Miniature
NPT-National Pipe Tapered