99 sizes
Metric (ISO)
ISO metric coarse and fine threads, M1 to M64, with the standard D − P tap drill.
Reference · 228 sizes
Thread size reference
Pick a thread system to browse every size. Each size page carries its dimensions, the recommended tap drill and clearance hole, a torque estimate and wrench sizes - all generated from the standard formulas.
99 sizes
Unified (UNC / UNF / UNEF)
Inch threads: UNC, UNF, UNEF and constant-pitch UN series, #0 to 2-1/2".
30 sizes
Pipe (NPT / BSPT / BSPP)
Tapered and parallel pipe threads: NPT, BSPT (R) and BSPP (G).
Guides · free
How to use these numbers
The size pages give you the figures. The guides explain where they come from - how tap drill sizes and thread engagement are worked out, what changes between a coarse and a fine pitch, how to identify a thread you cannot name, and why two torque charts for the same bolt disagree.