Threads Per Inch (TPI)

Threads Per Inch (TPI) is the count of thread crests within one inch of a fastener’s length in imperial systems. You use TPI to describe how coarse or fine a screw thread is. Lower TPI indicates coarse threads with fewer turns per inch, speeding assembly but reducing shear strength. Higher TPI indicates fine threads with more turns per inch, increasing clamp load and vibration resistance at the expense of longer installation times. Engineers and buyers rely on TPI to match fasteners to load requirements, torque tools, and mating components in mechanical and structural applications.