Thread Dimensions
Pitch, pitch diameter, minor diameters, thread depth, and tensile stress area for UNC/UNF and ISO metric threads — or any custom major and pitch.
One triangle,
every 60° thread.
The basic profile behind UN and ISO threads, and where charts differ.
The basic profile
Unified (ASME B1.1) and ISO metric (ISO 68-1) threads share the 60° basic profile, so the same formulas apply: fundamental triangle H = 0.866 × P; pitch diameter = D − 0.6495 × P; external minor diameter = D − 1.2269 × P; internal minor diameter = D − 1.0825 × P; external thread depth = 0.6134 × P. Inch pitch is 1 ÷ TPI. Every value is shown in the other unit system as well.
Tensile stress area
The area that bolt strength tables multiply by proof or tensile stress. ISO 898-1 uses π/4 × ((d2 + d3)/2)² — M10 gives 58.0 mm², M12 84.3 mm². ASME B1.1 uses π/4 × (D − 0.9743 × P)² — 1/4-20 gives 0.0318 in². The two constants differ slightly, so each system uses its own standard's formula here and the results match the printed tables.
What this is not
Basic (nominal) dimensions only: tolerance classes such as 6g/6H or 2A/2B, allowances, and go/no-go gauge limits come from the standards' tables and are not computed. The size list is the same one Tap Drill uses, cross-checked against the standard formulas and pairs on 17 September 2026 but not yet reviewed against the standard texts. Inputs stay in your browser; the same four anonymous usage counts as the rest of the site apply.