Thread Pitch and Thread Count (TPI)

TPI stands for Threads Per Inch. This is simply a count of the number of threads per inch measured along the length of a fastener. TPI is used only with American fasteners. Metric Fasteners use a thread Pitch (see below). In general smaller fasteners have finer threads, so the thread count is higher. For a table of standard US thread counts please see our US Threads Per Inch Table .

Metric fasteners are specified with a thread pitch instead of a thread count. The thread pitch is the distance between threads expressed in millimeters (measured along the length of the fastener). For example a thread pitch of 1.5 means that the distance between one thread and the next is 1.5mm. In general smaller fasteners have finer thread so they have lower thread pitch. For a table of standard metric thread pitchs please see our Metric Thead Pitch Table .

Thread count or pitch is normally measured using a Thread Gauge. You can use our printable PDF thread gauge or you can buy a thread gauge. If you will be measuring fasteners frequently, it is recommended that you purchase one of our inexpensive thread gauges, which are significantly easier to use.