Pick your Thread System and what you want to Calculate From — enter values like Thread Length, Number of Threads, TPI, Known Pitch, or Major Diameter — and the Thread Pitch Calculator works out your Thread Pitch along with Threads Per Inch, Pitch in inches, and Minor Diameter.
Thread Pitch
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Threads Per Inch (TPI)
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Pitch (inches)
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Minor Diameter
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Thread pitch is the distance between two adjacent threads on a threaded fastener. In metric threads, it's measured in millimeters, while in imperial threads, it's often expressed as threads per inch (TPI).
To find the thread pitch: divide 2 inches by 48 threads = 0.04167 inches pitch. Converting to metric: 2 inches × 25.4 mm/inch = 50.8 mm, then 50.8 mm ÷ 48 threads = 1.058 mm pitch.
Count the number of threads over a known length (like 1 inch or 25mm), then divide the length by the number of threads. For better accuracy, measure over a longer distance and use a magnifying glass.
Metric thread pitch is the distance between threads in millimeters. Imperial TPI (threads per inch) is the number of threads in one inch. To convert: Pitch (mm) = 25.4 ÷ TPI.
A thread pitch gauge is a precision tool with various thread profiles that you match against your fastener to determine the exact pitch. It's more accurate than measuring with a ruler and commonly used by machinists.
If you know the thread designation (like M8×1.25 or 1/4-20), the pitch is included in the specification. M8×1.25 means 8mm diameter with 1.25mm pitch, while 1/4-20 means 20 TPI.
UNC (Unified National Coarse) threads have fewer threads per inch for faster assembly, while UNF (Unified National Fine) threads have more threads per inch for greater holding strength and finer adjustment.
Yes, but they're not directly interchangeable due to different thread profiles. You can convert the pitch measurements: Imperial pitch (inches) = Metric pitch (mm) ÷ 25.4, and TPI = 25.4 ÷ Metric pitch (mm).