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Thread Pitch Chart

A reference chart to view the thread pitch for metric coarse, metric fine and extra fine and imperial fasteners UNC (unified national coarse) and UNF (unified national fine) and includes hard to find fasteners like BSW (British standard whitworth), BSF (British standard fine) and BA (British association). Laid out in diameter order with the smallest first, you can easily see the closest similar size across each different thread type working from left to right. This helps decide what fastener you have or if you need to substitute it for one that is available. Please note this chart has been complied to be a helpful resource and does not mean we carry the size or thread type in stock.

Measuring Threads by Pitch
Measuring Threads Per Inch (TPI)

METRIC THREADS
Pitch (mm)
Size	Coarse	Fine	Extra Fine
M1.6	0.35
M2	0.40

M2.5	0.45

M3	0.50

M3.5	0.60
M4	0.70

M5	0.80

M6	1.00

M7	1.00
M8	1.25	1.00
M10	1.50	1.25	1.00

M12	1.75	1.50	1.25
M14	2.00	1.50
M16	2.00	1.50

M18	2.50	1.50
M20	2.50	1.50
M22	2.50	1.50
M24	3.00	2.00	1.50
M27	3.00	2.00
M30	3.50	2.00
M33	3.50	2.00
M36	4.00	3.00
M39	4.00	3.00
M42	4.50
M45	4.50
M48	5.00
M52	5.00
M56	5.50
M60	5.50
M64	6.00
M72	6.00
M80	6.00

M90	6.00

M100	6.00

AMERICAN INCH THREADS
Threads per Inch (TPI)
Size	UNC	UNF	UN8
#0		80
#1	64	72
#2	56	64
#3	48	56
#4	40	48
#5	40	44

#6	32	40
#8	32	36

#10	24	32
#12	24	28

#1/4”	20	28

5/16”	18	24
3/8”	16	24
7/16”	14	20
1/2”	13	20
9/16”	12	18
5/8”	11	18


3/4”	10	16
7/8”	9	14
1”	8	14/12	8
1-1/8”	7	12	8
1-1/4”	7	12	8
1-3/8”	6	12	8
1-1/2”	6	12	8
1-5/8”			8

1-3/4”	5		8
1-7/8”	5		8
2”	4.5		8
2-1/4”	4.5		8

2-1/2”	4		8
2-3/4”	4		8
3”	4		8
3-1/4”	4		8
3-1/2”	4		8
3-3/4”	4		8
4”	4		8

BRITISH INCH THREADS
Threads per Inch (TPI)
Size	BSW	BSF	BA


8BA			59.1

6BA			47.9
1/8”	40
5BA			43
4BA			38.5
3BA			34.8
2BA			31.4
3/16”	24	32	32
1BA			28.2
0BA			25.4
1/4”	20	26
9/32”		26
5/16”	18	22
3/8”	16	20
7/16”	14	18
1/2”	12	16
9/16”	12	16
5/8”	11	14
11/16”		14

3/4”	10	12
7/8”	9	11
1”	8	10
1-1/8”	7	9
1-1/4”	7	9
1-3/8”	7	8
1-1/2”	6	8
1-5/8”	5	8

1-3/4”	5	7

2”	4.5	7
2-1/4”	4	6

2-1/2”	4	6
2-3/4”	3.5	6
3”	3.5	5
3-1/4”	3.25	5
3-1/2”	3.25	4.5
3-3/4”	3	4.5
4”	3	4.5

Download chart: Thread Pitch Chart