Free thread pitch calculator converts TPI to pitch & vice versa. Calculate thread pitch for imperial & metric threads. Instant results for machining, engineering & repairs.
Thread pitch is the distance between adjacent threads. It is calculated as the reciprocal of the number of threads per unit length:
A thread pitch calculator is a precision tool that converts threads per inch (TPI) to pitch measurements and vice versa, essential for engineers, machinists, and DIY enthusiasts working with threaded fasteners. Thread pitch represents the distance between adjacent thread crests and determines the compatibility of threaded connections in both imperial and metric systems.
This free thread pitch calculator instantly converts between threads per inch (TPI) and pitch measurements, eliminating manual calculations and preventing costly measurement errors in machining, engineering, and repair projects. Whether you're identifying replacement fasteners or programming CNC machines, accurate thread pitch calculations are crucial for proper fit and function.
Save time and ensure precision with our calculator that supports both imperial thread specifications (like UNC, UNF) and metric thread standards (ISO metric), making it the complete solution for all your thread measurement needs.
Thread pitch is the linear distance between adjacent thread crests (or roots) measured parallel to the thread axis. It represents how closely spaced the threads are and determines fastener compatibility. Thread pitch is measured in:
Key relationship: Thread pitch = 1 ÷ threads per unit length
This measurement is essential for proper fastener selection, machining operations, and ensuring threaded components fit together correctly.
In the imperial system, threads are typically specified by their diameter and number of threads per inch (TPI). For example, a 1/4"-20 screw has a 1/4-inch diameter with 20 threads per inch.
In the metric system, threads are specified by their diameter and pitch in millimeters. For example, an M6×1.0 screw has a 6mm diameter with a 1.0mm pitch.
The relationship between these measurements is straightforward:
It's important to distinguish between thread pitch and thread lead:
For single-start threads (the most common type), pitch and lead are identical. However, for multi-start threads, the lead is equal to the pitch multiplied by the number of starts.
The mathematical relationship between thread pitch and threads per unit length is based on a simple inverse relationship:
For imperial threads, the formula becomes:
For example, a thread with 20 TPI has a pitch of:
For metric threads, the formula is:
For example, a thread with 0.5 threads per mm has a pitch of:
Our thread pitch calculator provides instant, accurate conversions between TPI and pitch measurements. This free tool simplifies thread pitch calculations for professionals and DIY enthusiasts alike.
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A standard 1/4-inch UNC (Unified National Coarse) bolt has 20 threads per inch.
A standard M10 coarse thread has a pitch of 1.5mm.
A 3/8-inch UNF (Unified National Fine) bolt has 24 threads per inch.
A fine M8 thread has a pitch of 1.0mm.
Here are examples of how to calculate thread pitch in various programming languages:
1// JavaScript function to calculate thread pitch from threads per unit
2function calculatePitch(threadsPerUnit) {
3 if (threadsPerUnit <= 0) {
4 return 0;
5 }
6 return 1 / threadsPerUnit;
7}
8
9// JavaScript function to calculate threads per unit from pitch
10function calculateThreadsPerUnit(pitch) {
11 if (pitch <= 0) {
12 return 0;
13 }
14 return 1 / pitch;
15}
16
17// Example usage
18const tpi = 20;
19const pitch = calculatePitch(tpi);
20console.log(`A thread with ${tpi} TPI has a pitch of ${pitch.toFixed(4)} inches`);
211# Python functions for thread pitch calculations
2
3def calculate_pitch(threads_per_unit):
4 """Calculate thread pitch from threads per unit"""
5 if threads_per_unit <= 0:
6 return 0
7 return 1 / threads_per_unit
8
9def calculate_threads_per_unit(pitch):
10 """Calculate threads per unit from pitch"""
11 if pitch <= 0:
12 return 0
13 return 1 / pitch
14
15# Example usage
16tpi = 20
17pitch = calculate_pitch(tpi)
18print(f"A thread with {tpi} TPI has a pitch of {pitch:.4f} inches")
19
20metric_pitch = 1.5 # mm
21threads_per_mm = calculate_threads_per_unit(metric_pitch)
22print(f"A thread with {metric_pitch}mm pitch has {threads_per_mm:.4f} threads per mm")
231' Excel formula to calculate pitch from threads per inch
2=IF(A1<=0,0,1/A1)
3
4' Excel formula to calculate threads per inch from pitch
5=IF(B1<=0,0,1/B1)
6
7' Where A1 contains the threads per inch value
8' and B1 contains the pitch value
91// Java methods for thread pitch calculations
2public class ThreadCalculator {
3 public static double calculatePitch(double threadsPerUnit) {
4 if (threadsPerUnit <= 0) {
5 return 0;
6 }
7 return 1 / threadsPerUnit;
8 }
9
10 public static double calculateThreadsPerUnit(double pitch) {
11 if (pitch <= 0) {
12 return 0;
13 }
14 return 1 / pitch;
15 }
16
17 public static void main(String[] args) {
18 double tpi = 20;
19 double pitch = calculatePitch(tpi);
20 System.out.printf("A thread with %.0f TPI has a pitch of %.4f inches%n", tpi, pitch);
21
22 double metricPitch = 1.5; // mm
23 double threadsPerMm = calculateThreadsPerUnit(metricPitch);
24 System.out.printf("A thread with %.1fmm pitch has %.4f threads per mm%n",
25 metricPitch, threadsPerMm);
26 }
27}
281#include <iostream>
2#include <iomanip>
3
4// C++ functions for thread pitch calculations
5double calculatePitch(double threadsPerUnit) {
6 if (threadsPerUnit <= 0) {
7 return 0;
8 }
9 return 1 / threadsPerUnit;
10}
11
12double calculateThreadsPerUnit(double pitch) {
13 if (pitch <= 0) {
14 return 0;
15 }
16 return 1 / pitch;
17}
18
19int main() {
20 double tpi = 20;
21 double pitch = calculatePitch(tpi);
22 std::cout << "A thread with " << tpi << " TPI has a pitch of "
23 << std::fixed << std::setprecision(4) << pitch << " inches" << std::endl;
24
25 double metricPitch = 1.5; // mm
26 double threadsPerMm = calculateThreadsPerUnit(metricPitch);
27 std::cout << "A thread with " << metricPitch << "mm pitch has "
28 << std::fixed << std::setprecision(4) << threadsPerMm << " threads per mm" << std::endl;
29
30 return 0;
31}
32Thread pitch calculations are essential in various fields and applications:
While thread pitch is a fundamental measurement, there are alternative approaches to specifying and working with threads:
The development of standardized thread systems has been crucial to industrial progress, enabling interchangeable parts and global commerce.
The concept of screw threads dates back to ancient civilizations, with evidence of wooden screws used in olive and wine presses in Greece as early as the 3rd century BCE. However, these early threads were not standardized and were typically custom-made for each application.
The first attempt at thread standardization came from British engineer Sir Joseph Whitworth in 1841. The Whitworth thread system became the first nationally standardized thread system, featuring a 55-degree thread angle and standardized pitches for various diameters.
In the United States, William Sellers proposed a competing standard in 1864, featuring a 60-degree thread angle, which eventually evolved into the American National Standard. During World War II, the need for interchangeability between American and British threaded components led to the development of the Unified Thread Standard (UTS), which is still in use today.
The metric thread system, now governed by the ISO (International Organization for Standardization), was developed in Europe and has become the global standard for most applications. The ISO metric thread features a 60-degree thread angle and standardized pitches based on the metric system.
Early thread pitch measurements relied on manual counting and simple tools. The thread pitch gauge, a comb-like tool with multiple blades of different pitches, was developed in the late 19th century and remains in use today.
Modern measurement technologies include:
These advanced tools allow for precise measurement of thread parameters, including pitch, major diameter, minor diameter, and thread angle.
Accurately measuring thread pitch is crucial for proper identification and specification. Here are several methods used by professionals:
Thread pitch is calculated by dividing 1 by the threads per inch (TPI). The formula is: Pitch (inches) = 1 ÷ TPI. For example, a 20 TPI thread has a pitch of 1 ÷ 20 = 0.050 inches. This thread pitch calculation is essential for determining fastener compatibility.
Thread pitch is the distance between adjacent thread crests, while threads per inch (TPI) is the number of threads in one inch. They have an inverse relationship: pitch = 1/TPI and TPI = 1/pitch. Understanding both measurements is crucial for thread identification and selection.
To measure thread pitch without a specialized gauge:
Metric thread pitch is measured directly in millimeters (e.g., M10×1.5 has 1.5mm pitch), while imperial thread pitch is typically specified as threads per inch (e.g., 1/4"-20 has 20 TPI or 0.050" pitch). Both systems use the same basic calculation principles.
Yes, to convert metric to imperial thread pitch: TPI = 25.4 ÷ metric pitch (mm). To convert imperial to metric: metric pitch (mm) = 25.4 ÷ TPI. This conversion is essential when working with international fastener specifications.
Standard thread pitches vary by size:
Imperial (UNC - Unified National Coarse):
Metric (ISO standard):
Thread pitch affects fastener strength significantly. Fine threads (smaller pitch) provide:
Coarse threads (larger pitch) offer:
Thread pitch determines the cutting tool selection and machine settings for threading operations. CNC programmers must specify the correct pitch for:
Thread identification tools include:
American Society of Mechanical Engineers. (2009). ASME B1.1-2003: Unified Inch Screw Threads (UN and UNR Thread Form).
International Organization for Standardization. (2010). ISO 68-1:1998: ISO general purpose screw threads — Basic profile — Metric screw threads.
Oberg, E., Jones, F. D., Horton, H. L., & Ryffel, H. H. (2016). Machinery's Handbook (30th ed.). Industrial Press.
Bickford, J. H. (2007). Introduction to the Design and Behavior of Bolted Joints (4th ed.). CRC Press.
British Standards Institution. (2013). BS 3643-1:2007: ISO metric screw threads. Principles and basic data.
Deutsches Institut für Normung. (2015). DIN 13-1: ISO general purpose metric screw threads — Part 1: Nominal sizes for coarse pitch threads.
Society of Automotive Engineers. (2014). SAE J1199: Mechanical and Material Requirements for Metric Externally Threaded Fasteners.
Machinery's Handbook. (2020). Thread Systems and Designations. Retrieved from https://www.engineersedge.com/thread_pitch.htm
Ready to simplify your thread pitch calculations? Our free thread pitch calculator eliminates guesswork and prevents costly measurement errors in your projects. Whether you're working with imperial TPI or metric pitch measurements, get instant, accurate results for professional machining, engineering, and repair work.
Use our thread pitch calculator today to:
Calculate thread pitch now and experience the precision that professionals rely on for accurate threading operations and fastener specifications!
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