Thread Pitch / TPI Converter Online (Inch vs Metric)

Thread Pitch / TPI Converter (Inch vs Metric)

Inch threads are specified in threads per inch (TPI) while metric threads use pitch in millimeters - the two are reciprocals: P = 25.4 / TPI. Drawings say 1/4"-20, process sheets say M6x1.0, and the shop floor easily mixes them up. This online converter switches either side instantly, with a UNC coarse-thread reference table.

Warning: metric and inch threads with similar nominal sizes (1/4" vs M6: 6.35 vs 6.0 mm) share the 60-degree thread angle but differ in diameter and pitch - forced assembly ruins both threads. Always confirm the drawing system before purchasing or assembly.

UNF fine threads pack more TPI at the same diameter (1/4"-28 UNF, P=0.91 mm). For length and torque units use our unit converter. Zhuhai Jiali Hardware manufactures both metric and inch precision screws - contact us.