Tooth per inch (tpi)

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What is TPI?

TPI Sketch

Pitch is the axial distance between adjacent repeating features on a mechanical element. TPI is an imperial unit of measurement for pitch, commonly used in the United States. As its name suggests, it is the number of times in which the feature appears over a linear distance of 1″ (25.4 mm)

Mecahnical Compenents with a Pitch

Examples of mechanical elements with a pitch:

  • Screws / Threads.
  • Knurls..
  • Saw blades.
  • Milling Cutters.

TPI Conversion Calculator

TPI conververtion formulas

TPI vs linear pitch
\( \large TPI = \LARGE \frac {1}{P} \large \text { (P in Inches)} \)

\( \large TPI = \LARGE \frac {25.4}{P} \large \text { (P in mm)} \)

\( \large P = \LARGE \frac {1}{TPI} \large \text { (P in Inches)} \)

\( \large P = \LARGE \frac {25.4}{TPI} \large \text { (P in mm)} \)

TPI Convertion Chart

TPI Pitch (Inch) Pitch (mm)
2 0.5000 12.70
3 0.3333 8.47
4 0.2500 6.35
5 0.2000 5.08
6 0.1667 4.23
7 0.1429 3.63
8 0.1250 3.18
9 0.1111 2.82
10 0.1000 2.54
11 0.0909 2.31
12 0.0833 2.12
13 0.0769 1.95
14 0.0714 1.81
15 0.0667 1.69
16 0.0625 1.59
17 0.0588 1.49
18 0.0556 1.41
19 0.0526 1.34
20 0.0500 1.27
21 0.0476 1.21
22 0.0455 1.15
23 0.0435 1.10
24 0.0417 1.06
25 0.0400 1.02
26 0.0385 0.98
27 0.0370 0.94
28 0.0357 0.91
29 0.0345 0.88
30 0.0333 0.85
31 0.0323 0.82
32 0.0313 0.79
33 0.0303 0.77
34 0.0294 0.75
35 0.0286 0.73
36 0.0278 0.71
37 0.0270 0.69
38 0.0263 0.67
39 0.0256 0.65
40 0.0250 0.64
41 0.0244 0.62
42 0.0238 0.60
43 0.0233 0.59
44 0.0227 0.58
45 0.0222 0.56
46 0.0217 0.55
47 0.0213 0.54
48 0.0208 0.53
49 0.0204 0.52
50 0.0200 0.51
51 0.0196 0.50
52 0.0192 0.49
53 0.0189 0.48
54 0.0185 0.47
55 0.0182 0.46
56 0.0179 0.45
57 0.0175 0.45
58 0.0172 0.44
59 0.0169 0.43
60 0.0167 0.42
61 0.0164 0.42
62 0.0161 0.41
63 0.0159 0.40
64 0.0156 0.40
65 0.0154 0.39
66 0.0152 0.38
67 0.0149 0.38
68 0.0147 0.37
69 0.0145 0.37
70 0.0143 0.36
71 0.0141 0.36
72 0.0139 0.35
73 0.0137 0.35
74 0.0135 0.34
75 0.0133 0.34
76 0.0132 0.33
77 0.0130 0.33
78 0.0128 0.33
79 0.0127 0.32
80 0.0125 0.32
81 0.0123 0.31
82 0.0122 0.31
83 0.0120 0.31
84 0.0119 0.30
85 0.0118 0.30
86 0.0116 0.30
87 0.0115 0.29
88 0.0114 0.29
89 0.0112 0.29
90 0.0111 0.28
91 0.0110 0.28
92 0.0109 0.28
93 0.0108 0.27
94 0.0106 0.27
95 0.0105 0.27
96 0.0104 0.26
97 0.0103 0.26
98 0.0102 0.26
99 0.0101 0.26
100 0.0100 0.25
101 0.0099 0.25
102 0.0098 0.25
103 0.0097 0.25
104 0.0096 0.24
105 0.0095 0.24
106 0.0094 0.24
107 0.0093 0.24
108 0.0093 0.24
109 0.0092 0.23
110 0.0091 0.23
111 0.0090 0.23
112 0.0089 0.23
113 0.0088 0.22
114 0.0088 0.22
115 0.0087 0.22
116 0.0086 0.22
117 0.0085 0.22
118 0.0085 0.22
119 0.0084 0.21
120 0.0083 0.21
121 0.0083 0.21
122 0.0082 0.21
123 0.0081 0.21
124 0.0081 0.20
125 0.0080 0.20
126 0.0079 0.20
127 0.0079 0.20
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