Thread Identification Chart

Imperial (US) and Metric Thread Identification Charts:

US and Metric Thread Identification Chart pdf
  • US and Metric Thread Identification Chart (PDF) - Print Friendly, 136Kb
  • This Thread Identification Chart provides a visual guide to help identify different US and Metric fastener threads. It includes information such as Thread Per Inch, Thread Pitch, Diameter, and Thread type. This can be useful for individuals who need to select the correct fasteners for a specific application or for those who work with fasteners regularly.

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To help you work with fasteners or have a general interest in understanding the differences between thread pitch and threads per inch. We provide explanations of these concepts and how they relate to various fastener types, along with useful charts and diagrams to aid in visual understanding. You can gain a better understanding of how thread pitch and TPI impact the functionality and compatibility of fasteners, ultimately help you to select the right fastener for your specific application/project. Please read our complete guide about Thread Pitch Vs. Threads Per Inch

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Acronyms:
  • UNC - Unified National Coarse
  • UNF - Unified National Fine
  • UNEF - Unified National Extra Fine
  • UNM - Unified National Miniature
  • NPT - National Pipe Tapered
  • * - ISO Standard-1st Choice
  • ** - ISO Standard-2nd Choice
  • *** - ISO Standard-3rd Choice
  • X - DIN (German Standard)
Basic Major Diameter US Standard Metric
Inch mm Nominal
Diameter
mm
 Thread Per Inch (TPI) Nominal
Diameter
mm		 Standards Pitch in mm
UNC UNF UNEF UNM Coarse Fine M Taper
.0118 0.30 0.30 318 X 0.075
.0138 0.35 0.35 282 * 0.080
.0146 0.37 254
.0157 0.40 0.40 *X 0.100
.0165 0.42
.0177 0.45 0.45 254 ** 0.100
.0189 0.48
.0197 0.50 0.50 203 *X 0.125
.0209 0.53 160
.0213 0.54
.0217 0.55 0.55 203 ** 0.125
.0236 0.60 0.60 169 *X 0.150
.0244 0.62
.0276 0.70 0.70 145 0.175
.0311 0.79
.0315 0.80 0.80 127 *X 0.200
.0340 0.86 120
.0354 0.90 0.90 113 **X 0.225
.0394 1.00 1.00 102 *X 0.250 0.2
.0433 1.10 1.10 102 ** 0.250 0.2
.0470 1.19 90 96
.0472 1.20 1.20 *X 0.250 0.2
.0512 1.30
.0551 1.40 1.40 85 **X 0.300 0.2
.0591 1.50 1.50 0.300
.0600 1.52 80
.0629 1.60 1.60 * 0.350 0.2
.0669 1.70 1.70 X 0.350 0.2,0.25
.0709 1.80 1.80 ** 0.350 0.2
.0730 1.85 #1 64 72
.0748 1.90
.0787 2.00 *X 0.400 0.25,0.35
.0860 2.18 #2 56 64
.0866 2.20 2.20 ** 0.450 0.25
.0906 2.30 2.30 X 0.400 0.25,0.35
.0984 2.50 2.50 * 0.45 0.35
.0990 2.51 #3 48 56
.1024 2.60 2.60 X 0.45 0.25,0.35
.1102 2.80
.1120 2.84 #4 40 48
.1181 3.00 3.00 *X 0.50 0.35
.1250 3.18 #5 40 44
.1260 3.20
.1380 3.50 #6 32 40 3.50 **X 0.60 0.35,0.5
.1417 3.60
.1575 4.00 4.00 *X 0.70 0.5,0.75
.1614 4.10
.1640 4.17 #8 32 36
.1772 4.50 4.50 ** 0.75 0.5
.1850 4.70
.1875 4.76
.1900 4.83 #10 24 32
.1969 5.00 5.00 *X 0.80 0.5, 0.75, 0.90
.2087 5.30
.2160 5.49 #12 24 28 32
.2165 5.50 5.50 *** 0.90 0.5
.2188 5.56
.2362 6.00 6.00 *X 1.00 0.5, 0.75
.2500 6.35 1/4 20 28 32
.2756 7.00 7.00 ***X 1.00 0.5, 0.75
.2812 7.14
.3125 7.94 5/16 18 24 32
.3125 7.94 1/16 27
.3150 8.00 8.00 *X 1.25 0.5, 0.75, 1
.3543 9.00 9.00 ***X 1.25 0.75, 1
.3750 9.53 3/8 16 24 32 1
.3830 9.73
.3937 10.00 10.00 *X 1.5 0.75, 1, 1.25
.4050 10.29 1/8 27
.4331 11.00 11.00 ***X 1.5 0.75, 1, 1.25
.4375 11.11 7/16 14 20 28
.4724 12.00 12.00 *X 1.75 1, 1.25, 1.5 1.5
.5000 12.70 1/2 13 20 28
.5180 13.16
.5400 13.72 1/4 18
.5512 14.00 14.00 **X 2.00 1, 1.25, 1.5
.5625 14.29 9/16 12 18 24
.6250
.6299 16.00 16.00 *X 2.00 1, 1.5 1.5
.6560 16.66
.6750 17.15 3/8 18
.6875 17.46 11/16 24
.7087 18.00 18.00 **X 2.5 1, 1.5, 2 1.5
.7500 19.05 3/4 10 16 20
.7874 20.00 20 *X 2.5 1, 1.5, 2 1.5
.8125 20.64 13/16 20
.8250 20.96
.8400 21.34 1/2 14
.8661 22.00 22 **X 2.5 1, 1.5, 2 1.5
.8750 22.23 7/8 9 14 20
.9020 22.91
.9375 23.81 15/16 20
.9449 24.00 24 *X 3 1, 1.5, 2
1.0000 25.40 1 8 14 20
1.0236 26.00 26 ***X 1.5 1.5
1.0410 26.44
1.0500 26.67 3/4 14
1.0625 26.99 1-1/16 18
1.0630 27.00 27 **X 3 1, 1.5, 2
1.1250 28.58 1-1/8 7 12 18
1.1811 30.00 30 *X 3.5 1, 1.5, 2, 3
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 32 ***X 1.5, 2
1.2992 33.00 33 **X 3.5 1.5, 2, 3
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 35 ***X 1.5
1.4173 36.00 36 *X 4 1.5, 2, 3
1.4375 36.51 1-7/16 18
1.4920 37.90 1.5
1.4961 38.00 38 ***X
1.5000 38.10 1-1/2 6 12 18
1.5354 39.00 39 **X 4 1.5, 2, 3
1.5625 39.69 1-9/16 18
1.5748 40.00 40 ***X 1.5, 2, 3
1.6250 41.28 1-5/8 18
1.6500 41.91
1.6535 42.00 42 *X 4.5 1.5, 2, 3, 4
1.6600 42.16 1-1/4 11-1/2
1.6875 42.86 1 11/16 18
1.7450 44.32