Thread calculator — ISO 965-1 and ASME B1.1

This free thread calculating tool computes the limits of size of metric threads (M2 to M300, tolerance classes 6g, 6H, 5g6g…) per ISO 965-1, and of Unified inch threads (UNC, UNF, UNEF, classes 1A to 3B, #0 to 4 in) per ASME B1.1: major, pitch and minor diameters, with the tolerance mid-point and IT interval.

3-wire measurement

The measurement over three wires (thread wires, pin gauges) is computed for the best wire (0.577 × pitch), for commercial wire-kit sizes graded usable / borderline / out of range, or for a custom wire diameter — including a gauge block (e.g. 0.100 in) and the full calculation detail, printable as a one-page PDF report.

Gaging and tapping

Alongside GO/NOGO thread gages and Asterion Gage instruments, the tool also recommends the 75% engagement tap drill for internal threads. Works offline, in French and English, in millimetres and inches.