Standard Thread Pitch Chart: Metric & Imperial

Standard Chart for Thread Pitch 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)

Nominal DiameterThread Pitch (i.e., Threads per Inch)
Coarse Threads (UNC)Fine Threads (UNF)
M10.250.2
M1.20.250.2
M1.60.350.2
M20.40.25
M2.50.450.35
M30.50.35
M3.50.60.35
M40.70.5
M50.80.5
M610.75
M81.251
M101.51.25
M121.751.25
M1421.5
M1621.5
M182.51.5
M202.51.5
M222.51.5
M2432
M2732
M303.52
(M33)3.52
M3643
(M39)43
M424.53
(M45)4.53
M4853

Imperial Standard Thread Pitch Table

(Including Coarse and Fine Threads)

Nominal DiameterDiameter SizeThread Pitch (i.e., Threads per Inch)
inchmmCoarse Threads (UNC)Fine Threads (UNF)
0#0.061.52480
1#0.0731.8546472
2#0.0862.1845664
3#0.0992.5154856
4#0.1122.8454048
5#0.1253.1754044
6#0.1383.5053240
8#0.1644.1663236
10#0.194.8262432
12#0.2165.4862428
1/4″0.256.352028
5/16″0.31257.9381824
3/8″0.3759.5251624
7/16″0.437511.1131420
1/2″0.512.71320
9/16″0.562514.2881218
5/8″0.62515.8751118
3/4″0.7519.051016
7/8″0.87522.225914
1″125.4812
1-1/8″1.12528.575712
1-1/4″1.2531.75712
1-3/8″1.37534.925612
1-1/2″1.538.1612
1-3/4″1.7544.455
2″250.84.5
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Shane
Author

Shane

Founder of MachineMFG

As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.

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