# Tooth per inch (tpi)

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## What is TPI?

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)

Examples of mechanical elements with a pitch:

• Knurls..
• Milling Cutters.

## TPI conververtion formulas

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

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

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

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

## 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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