🔩 Thread Pitch Calculator
Calculate thread pitch from threads per inch
Number of threads per inch
How to Use This Calculator
Select Calculation Type
Choose to calculate from threads per inch (TPI) or from thread pitch. Most common is calculating pitch from TPI.
Enter TPI or Pitch
If calculating from TPI, enter threads per inch (e.g., 13 for 1/2-13 UNC). If calculating from pitch, enter pitch in inches.
Optional: Enter Major Diameter
If calculating from pitch, optionally enter major diameter to calculate pitch diameter. This helps with thread design.
Calculate and Review
Click "Calculate Thread Pitch" to see thread pitch in inches and millimeters, threads per inch, and pitch diameter (if major diameter provided).
Formula
Thread Pitch = 1 / Threads Per Inch (TPI)
Threads Per Inch = 1 / Thread Pitch
Pitch Diameter = D - 0.6495 × P (if major diameter provided)
Example 1: From TPI (13 TPI)
Step 1: Thread Pitch = 1 / TPI = 1 / 13 = 0.0769"
Step 2: Pitch (mm) = 0.0769 × 25.4 = 1.954 mm
Example 2: From Pitch (P = 0.0769", D = 0.500")
Step 1: TPI = 1 / P = 1 / 0.0769 = 13 TPI
Step 2: Pitch Diameter = D - 0.6495 × P = 0.500 - 0.6495 × 0.0769 = 0.450"
About Thread Pitch Calculator
The Thread Pitch Calculator is an essential tool for machinists, mechanical engineers, and thread designers who need to calculate thread pitch from threads per inch (TPI) or vice versa. This calculator implements standard thread pitch formulas for unified, metric, ACME, and buttress threads, helping you determine thread specifications and ensure proper thread engagement.
When to Use This Calculator
- Thread Design: Calculate thread pitch for thread design and manufacturing
- Thread Measurement: Convert between TPI and pitch for thread inspection
- Fastener Selection: Determine thread pitch for fastener selection
- Thread Analysis: Analyze thread pitch and dimensions
- Educational Use: Learn and understand thread pitch calculations
Why Use Our Calculator?
- ✅ Dual Calculation Modes: Supports TPI-to-pitch and pitch-to-TPI calculations
- ✅ Multiple Thread Types: Supports Unified, Metric, ACME, and Buttress threads
- ✅ Complete Units: Shows pitch in inches and millimeters
- ✅ Pitch Diameter: Calculates pitch diameter if major diameter provided
- ✅ Time Savings: Instant calculations eliminate manual math
Understanding Thread Pitch
Basic Principle: Thread pitch is the distance between adjacent thread crests. For unified threads, pitch = 1 / TPI (threads per inch). For example, 13 TPI = 1/13 = 0.0769". For metric threads, pitch is specified directly in millimeters (e.g., M12×1.75 has pitch = 1.75 mm).
TPI Conversion: Threads Per Inch (TPI) and thread pitch are inversely related: TPI = 1 / Pitch, Pitch = 1 / TPI. Higher TPI means finer threads (smaller pitch), lower TPI means coarser threads (larger pitch). The calculator converts between TPI and pitch automatically.
Standard Pitches: Standard unified thread pitches: 1/2-13 UNC (pitch = 0.0769"), 1/2-20 UNF (pitch = 0.050"), 3/8-16 UNC (pitch = 0.0625"). Standard metric pitches: M12×1.75 (pitch = 1.75 mm), M12×1.5 (pitch = 1.5 mm), M10×1.5 (pitch = 1.5 mm).
Tips for Best Results
- Accurate TPI: Count threads per inch accurately for precise pitch calculation
- Correct Pitch: Measure thread pitch accurately for TPI calculation
- Verify with Standards: Check thread standards (ANSI, ISO) for exact values
- Consider Thread Type: Select appropriate thread type for accurate calculations
- Use Major Diameter: Provide major diameter to calculate pitch diameter
Frequently Asked Questions
How do I calculate thread pitch from TPI?
Thread Pitch = 1 / Threads Per Inch (TPI). For example, 13 TPI = 1/13 = 0.0769", 20 TPI = 1/20 = 0.050". The calculator does this automatically. Thread pitch is the distance between adjacent thread crests in inches.
How do I calculate TPI from thread pitch?
Threads Per Inch (TPI) = 1 / Thread Pitch. For example, pitch = 0.0769": TPI = 1 / 0.0769 = 13 TPI. The calculator supports both TPI-to-pitch and pitch-to-TPI calculations automatically.
What is the difference between thread pitch and TPI?
Thread pitch is the distance between adjacent thread crests in inches, while TPI (threads per inch) is the number of threads per inch. They are inversely related: Pitch = 1 / TPI, TPI = 1 / Pitch. Higher TPI means finer threads (smaller pitch), lower TPI means coarser threads (larger pitch).
What are standard thread pitches?
Standard unified thread pitches: 1/2-13 UNC (0.0769"), 1/2-20 UNF (0.050"), 3/8-16 UNC (0.0625"), 1/4-20 UNC (0.050"). Standard metric pitches: M12×1.75 (1.75 mm), M12×1.5 (1.5 mm), M10×1.5 (1.5 mm), M8×1.25 (1.25 mm). Thread pitch varies by size and thread series (UNC, UNF, UNEF).
Can I calculate pitch diameter from pitch?
Yes, if you provide major diameter, the calculator calculates pitch diameter using Pitch Diameter = Major Diameter - (0.6495 × Thread Pitch). For example, D = 0.500", P = 0.0769": PD = 0.500 - 0.6495 × 0.0769 = 0.450". This helps with thread design and measurement.