Calculate thread pitch, measured threaded span, pitch intervals, lead and starts, or convert metric pitch to TPI for common screw threads in mm, cm or inches.

Thread Pitch Formula

The following formula converts threads per inch to axial thread pitch.

P = 1 / n

Where P is the thread pitch (in)
n is the number of threads per inch

To calculate the thread pitch, take the inverse value of the number of threads per inch.

Thread Pitch Definition

What is a thread pitch? A thread pitch is defined as the axial spacing between adjacent thread crests. For a measured span, divide by the number of pitch intervals; 11 crests span 10 intervals.

Example Problem

How to calculate a thread pitch?

First, determine the measured threaded span.
For this example, the measured threaded span is 12 inches.
Next, count the pitch intervals across that span.
The span contains 24 pitch intervals (25 crest positions).
Next, determine the threads per inch.
Dividing the number of threads by the total length, we get 2 threads per inch.
Finally, calculate the thread pitch.
Using the formula P=1/n we find the pitch to be 1/2 = .5 inches.

FAQ

Is thread pitch metric? Thread pitch can be described using metric or imperial units. The definition of thread pitch is only the inverse of the threads per distance; therefore, it does not require a specific unit of measure.

Can you change the thread pitch? In order to change a thread pitch, you must change both the screw thread and mating thread in the hole so that they match and have the same pitch. They will not fit properly with different pitches.

Should I use a coarse or fine thread pitch? Choose the specified mating thread and applicable design standard. Strength and stripping resistance also depend on diameter, engagement, materials and loading; this pitch calculator does not select a safe fastener.