This external screw thread calculator finds the key dimensions of a 60° ISO/UN thread from the major diameter and pitch. Enter both above to get the pitch diameter, minor diameter, and thread depth.
How are thread dimensions calculated?
Pitch diameter = d − 0.6495 × P Minor diameter = d − 1.2269 × P Thread depth = 0.6134 × P Thread height (H) = 0.866 × P
- d — major (nominal) diameter, P — thread pitch
Example calculation
For an M10 × 1.5 thread (d = 10 mm, P = 1.5 mm):
- Pitch diameter = 10 − 0.6495 × 1.5 = 9.026 mm
- Minor diameter = 10 − 1.2269 × 1.5 = 8.160 mm
- Thread depth = 0.6134 × 1.5 = 0.920 mm
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Frequently Asked Questions
How do I calculate screw thread pitch diameter?
For a 60-degree ISO or UN thread, subtract 0.6495 times the pitch from the major diameter. For M10x1.5 that is 10 minus 0.974, or 9.026 mm.
What is the minor diameter of an external thread?
It is the major diameter minus 1.2269 times the pitch for a rounded-root external thread. For M10x1.5 that is about 8.16 mm.
What is thread depth?
The external thread depth is 0.6134 times the pitch for a standard 60-degree thread form, about 0.92 mm for a 1.5 mm pitch.