Thread Calculator
Plan your materials specifications project with our free thread calculator. Get precise measurements, material lists, and budgets.
Reviewed by Abdullah, Technical Content Specialist
Formula
Pitch Dia = D - 0.6495P | Minor Dia = D - 1.2269P | Tap Drill = D - P
For ISO metric threads with 60-degree profile: Pitch diameter = Major diameter - 0.6495 x Pitch. Minor diameter = Major diameter - 1.2269 x Pitch. Tap drill size for 75% thread = Major diameter - Pitch. Thread height H = 0.866025 x Pitch. These formulas derive from the standard 60-degree thread triangle geometry.
Worked Examples
Example 1: M10 x 1.5 Thread Dimensions
Problem:Calculate all thread dimensions for an M10 x 1.5 ISO metric thread.
Solution:H = 0.866 x 1.5 = 1.299 mm\nPitch Dia = 10 - 0.6495 x 1.5 = 9.026 mm\nMinor Dia = 10 - 1.2269 x 1.5 = 8.160 mm\nTap Drill = 10 - 1.5 = 8.5 mm\nTensile Area = pi/4 x ((9.026+8.160)/2)^2 = 57.99 mm2
Result:Pitch Dia: 9.026 mm, Minor Dia: 8.160 mm, Tap Drill: 8.5 mm
Example 2: M6 x 1.0 for Machine Screws
Problem:Find thread dimensions and tap drill for M6 x 1.0.
Solution:Pitch Dia = 6 - 0.6495 x 1.0 = 5.351 mm\nMinor Dia = 6 - 1.2269 x 1.0 = 4.773 mm\nTap Drill = 6 - 1.0 = 5.0 mm
Result:Pitch Dia: 5.351 mm, Tap Drill: 5.0 mm
References
Reviewed by Abdullah, Technical Content Specialist · Editorial policy