Thread Pitch Calculator

Convert threads per inch to pitch (the distance from one thread crest to the next).

How the Math Works

The Thread Pitch Calculator uses a straightforward mathematical relationship between thread pitch and threads per inch (TPI). When you know the TPI, the pitch in inches is calculated by dividing 1 by the TPI value (pitch = 1 ÷ TPI). For metric measurements, the formula multiplies the conversion factor of 25.4 mm per inch by dividing it by TPI (pitch in mm = 25.4 ÷ TPI). This inverse relationship reflects how more threads per inch result in a smaller individual thread height, and fewer threads per inch mean taller, more widely spaced threads.

Practical Applications

To use this calculator practically, first determine whether you're working with imperial or metric measurements. For imperial threads, count how many threads fit within a 1-inch segment or use a thread pitch gauge. Enter this TPI value into the calculator to instantly find the pitch measurement. For metric work, you can either convert your TPI result by multiplying by 25.4, or use the calculator's direct mm conversion. This is essential when selecting taps, dies, or cutting tools, as these accessories are sized specifically to match your thread's pitch specification.

Day-to-Day Use

This calculator becomes invaluable in everyday workshop scenarios where precision threading matters. Whether you're repairing a stripped bolt, selecting the right drill bit size for threading, or choosing the appropriate tap and die set, quickly converting between TPI and pitch saves time and prevents costly mistakes. It's particularly useful for DIY enthusiasts working on furniture assembly, automotive repairs, or plumbing fixtures, where understanding thread specifications ensures proper part compatibility and secure fastening connections.

Worked example

20 TPI → 0.05 in (1.27 mm) pitch.

FAQ