Thread Pitch and Thread Count (TPI)
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.
Measuring Thread Count and Thread Pitch
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.