Standard Thread Pitch Chart: Metric & Imperial

Thread Pitch: Also known as screw pitch, it refers to the axial distance between two corresponding points on the median line of adjacent threads, or the distance between adjacent crests or troughs.

Metric thread pitch is directly marked with distance (in millimeters, mm). For example, in M8*1.25, the 1.25 indicates that the thread pitch for M8 is 1.25MM.

Sometimes, out of habit, people tend to omit the thread pitch for commonly used metric threads, such as M8, which implies that the thread pitch is 1.25MM by default.

However, it’s best to avoid abbreviation to prevent unnecessary misunderstanding.

The thread pitch of a British or Imperial nut is marked by the number of threads contained within each inch.

For example, in 1/4-20, the 20 indicates that there are 20 threads per inch, which is approximately equivalent to 1.27mm in metric units.

However, it is not indicated as 1.27. For standard threads with a diameter less than 1/4 inch, the diameter is no longer indicated as a fraction like “1/4,” but is indicated by the number, as seen in 10#-24, 8#-32, etc.

Metric Thread Pitch Standard Table

(Including Coarse and Fine Threads)

Units are in millimetres (mm)

Imperial Standard Thread Pitch Table

(Including Coarse and Fine Threads)