Inches to threads per inch
Type a value in in to get it in TPI instantly.
That's 169× as coarse as a coarse structural thread — nothing on our list beats it. Ten millimeters of travel takes about 0.01969 turns.
Convert the other way: TPI to in
What it means
How coarse is that thread?
Pitch is only half the story: a thread also has a diameter and a flank angle. Metric threads use 60°, as do Unified threads, but British Whitworth uses 55°, so they never interchange.
The math
How to convert in to TPI
Pitch and threads per inch are reciprocals: mm = 25.4 ÷ TPI, and TPI = 25.4 ÷ mm. A finer thread means more threads per inch and a smaller pitch.
Example: 20 in = 0.05 TPI.
Every unit
Your pitch in every unit
Tables
in to TPI conversion table
| in | TPI |
|---|---|
| 4 in | 0.25 TPI |
| 6 in | 0.166667 TPI |
| 8 in | 0.125 TPI |
| 10 in | 0.1 TPI |
| 11 in | 0.0909091 TPI |
| 13 in | 0.0769231 TPI |
| 14 in | 0.0714286 TPI |
| 16 in | 0.0625 TPI |
| 18 in | 0.0555556 TPI |
| 20 in | 0.05 TPI |
| 24 in | 0.0416667 TPI |
| 28 in | 0.0357143 TPI |
| 32 in | 0.03125 TPI |
| 40 in | 0.025 TPI |
TPI to in conversion table
| TPI | in |
|---|---|
| 4 TPI | 0.25 in |
| 6 TPI | 0.166667 in |
| 8 TPI | 0.125 in |
| 10 TPI | 0.1 in |
| 11 TPI | 0.0909091 in |
| 13 TPI | 0.0769231 in |
| 14 TPI | 0.0714286 in |
| 16 TPI | 0.0625 in |
| 18 TPI | 0.0555556 in |
| 20 TPI | 0.05 in |
| 24 TPI | 0.0416667 in |
| 28 TPI | 0.0357143 in |
| 32 TPI | 0.03125 in |
| 40 TPI | 0.025 in |
Quick answers
Quick answers
- How many TPI is 1 in?
- 1 in is 1 TPI.
- How many TPI is 10 in?
- 10 in is 0.1 TPI.
- How many TPI is 20 in?
- 20 in is 0.05 TPI.
The units
About these units
Inches (in)
The pitch expressed in inches, used on some US machine-tool charts.
Threads per inch (TPI)
The imperial measure: how many threads fit in one inch.
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