Thread Pitch Calculator

Work out thread pitch instantly with clear inputs, formula shown and shareable results.

About Thread Pitch Calculator

Pitch is the axial distance between adjacent thread crests and is simply the reciprocal of threads per inch. For a 60 degree unified thread the basic minor diameter is the major diameter less 1.299 times the pitch, which is the figure behind tap drill selection.

Formulas

Pitch

Pitch in = 1 / threads per inch; mm = pitch x 25.4

Minor diameter

Basic minor = major - 1.299 x pitch

Worked example

With the default values below, Thread Pitch Calculator returns Thread pitch of 0.05000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Threads per inchminimum 1: 20
Measured thread lengthminimum 0.05 in: 1 in
Major diameterminimum 0.02 in: 0.25 in

Results

Thread pitch: 0.05000 in
Pitch in millimetres: 1.2700 mm
Threads in measured length: 20.0
Basic minor diameter: 0.18505 in

Step by step

1Values used
2Pitch
3Minor diameter
4Thread pitch= 0.05000 in
5Pitch in millimetres= 1.2700 mm
6Threads in measured length= 20.0
7Basic minor diameter= 0.18505 in

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Thread Pitch figure worked out?

Pitch in = 1 / threads per inch; mm = pitch x 25.4. Pitch is the axial distance between adjacent thread crests and is simply the reciprocal of threads per inch.

Is coarse or fine thread stronger?

Fine threads have slightly more tensile area and resist loosening better under vibration, but coarse threads tolerate damage and coatings far better and are less likely to cross-thread.

What values do I need to enter?

This calculator takes 3 inputs: Threads per inch, Measured thread length, Major diameter. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.