What is thread pitch?

Thread pitch is the axial distance between adjacent thread crests, measured in inches (imperial) or millimeters (metric). It is the reciprocal of TPI: pitch = 1 / TPI.

What is the difference between pitch and lead?

Pitch is the distance between adjacent threads. Lead is the axial distance a screw advances in one full revolution. For a single-start thread lead equals pitch. For a double-start thread lead equals 2 × pitch.

How do I read a metric thread designation like M10x1.5?

The "M" means metric, the number after M is the nominal diameter in mm, and the number after the × is the pitch in mm. M10x1.5 means a 10 mm diameter thread with 1.5 mm between crests.

The helix angle (also called lead angle) is the angle the thread helix makes with a plane perpendicular to the screw axis. It is calculated as arctan(lead / (π × diameter)).

Can I use this for multi-start threads?

Yes. Enter the number of starts and the calculator multiplies pitch by that number to give you the correct lead and helix angle.

What are common metric thread pitches for M10?

M10 coarse pitch is 1.5 mm (M10x1.5). Fine pitches are 1.25 mm and 1.0 mm. Coarse pitch is most common for general fastening.

Thread Pitch Calculator

Name: Thread Pitch Calculator
Availability: InStock
Author: Nham Vu

Convert threads-per-inch (TPI) to pitch in inches or calculate metric thread pitch, lead, and helix angle instantly.

Threads Per Inch (TPI) Nominal Diameter (inches) — for helix angle

Number of Starts — 1 for standard threads

Common Metric Coarse Threads

Enter thread parameters on the left to see results.

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Summary

Convert threads-per-inch (TPI) to pitch in inches or calculate metric thread pitch, lead, and helix angle instantly.

How it works

Choose Imperial mode and enter TPI, or choose Metric mode and enter the diameter and pitch directly.
For multi-start threads, set the number of starts (lead = pitch × starts).
The calculator instantly shows pitch in both inches and millimeters.
Lead (axial advance per full turn) is displayed alongside the helix angle.
Results update in real time as you type — no button press needed.

Use cases

Identify the correct replacement bolt or nut by calculating thread pitch from TPI.
Verify a metric screw designation before machining or purchasing.
Determine lead and helix angle for CNC thread-milling operations.
Cross-reference imperial and metric thread standards on mixed-fastener projects.
Calculate multi-start thread lead for power screws and lead screws.
Confirm thread pitch when reading prints in mixed unit systems.
Help students learn the relationship between TPI, pitch, and helix angle.
Quick reference for machinists, engineers, and builders on the shop floor.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu