Unified thread calculator finds tap drill, pitch diameter, and minor diameter for a standard UN/UNC/UNF thread from its major diameter and threads per inch (TPI).
How it works
Unified (inch) threads are specified by major diameter and TPI rather than pitch directly, so pitch is first derived as 1 divided by TPI before the pitch and minor diameter formulas are applied. As with metric threads, a finer TPI removes less material and leaves a stronger, shallower thread profile.
FAQ
What’s the difference between UNC and UNF for the same diameter? UNC (coarse) uses fewer threads per inch and cuts a deeper thread, generally preferred for general-purpose fastening and easier tapping in softer materials. UNF (fine) uses more threads per inch for a shallower thread, often chosen for thin materials or where finer positioning is needed.
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