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UTS Conversion | UNC Thread & UNF Thread Conversions

The pitch of a screw is defined by the angle of its threads - a coarse pitch will have a more obtuse thread angle, whereas a fine pitch will have a shallower thread angle, resulting in a greater number of threads on the screw itself, and a more secure fastening.

The Unified Thread Standard is an imperial thread standard used across the majority of Accu's imperial fastener ranges. Components using UTS threads generally fall into two categories, UNC (Unified Coarse) and UNF (Unified Fine).  UNEF (Unified Extra Fine) can also be made available on components which are manufactured to order. For the tooling used to identifying unknown thread types, please see Accu's ranges of UNS Thread Gauges.

Sizes within the Unified Thread Standard are designated using two numbers – the first represents the major diameter of the thread, and the second represents the pitch of the screw thread in threads per inch (TPI).

For instance, a UTS thread of 1/4-20 will have a diameter of 1/4 inch, and 20 threads per inch.

For thread sizes smaller than 1/4 inch, a numerical size such as No.1 (Or #1) is used.

For more general information on the conversion between metric and imperial measurements, please see our Metric to Imperial Conversion Table. We also have a page specifically for ISO Metric Thread Dimensions.

Major Diameter (inch/mm) Thread Density (d) and Thread Pitch (p)
Coarse Pitch (UNC) Fine Pitch (UNF) Extra Fine Pitch (UNEF)
d (TPI) p (inch/mm) d (TPI) p (inch/mm) d (TPI) p (inch/mm)
No. 0 0.0600 / 1.5240 N/A 80 0.12500 / 0.3175 N/A
No. 1 0.0730 / 1.8542 64 0.015625 / 0.3969 72 0.013888 / 0.3528 N/A
No. 2 0.0860 / 2.1844 56 0.017857 / 0.4536 64 0.015625 / 0.3969 N/A
No. 3 0.0990 / 2.5146 48 0.020833 / 0.5292 56 0.017857 / 0.4536 N/A
No. 4 0.1120 / 2.8448 40 0.025000 / 0.6350 48 0.020833 / 0.5292 N/A
No. 5 0.1250 / 3.1750 40 0.025000 / 0.6350 44 0.022727 / 0.5773 N/A
No. 6 0.1380 / 3.5052 32 0.031250 / 0.7938 40 0.025000 / 0.6350 N/A
No. 8 0.1640 / 4.1656 32 0.031250 / 0.7938 36 0.027778 / 0.7056 N/A
No. 10 0.1900 / 4.8260 24 0.041667 / 1.0583 32 0.031250 / 0.7938 N/A
No. 12 0.2160 / 5.4864 24 0.041667 / 1.0583 28 0.035714 / 0.9071 32 0.031250 / 0.7938
1/4 0.2500 / 6.3500 20 0.050000 / 1.2700 28 0.035714 / 0.9071 32 0.031250 / 0.7938
5/16 0.3125 / 7.9375 18 0.055556 / 1.4111 24 0.041667 / 1.0583 32 0.031250 / 0.7938
3/8 0.3750 / 9.5250 16 0.062500 / 1.5875 24 0.041667 / 1.0583 32 0.031250 / 0.7938
7/16 0.4375 / 11.1125 14 0.071428 / 1.8143 20 0.050000 / 1.2700 28 0.035714 / 0.9071
1/2 0.5000 / 12.7000 13 0.076923 / 1.9538 20 0.050000 / 1.2700 28 0.035714 / 0.9071
9/16 0.5625 / 14.2875 12 0.083333 / 2.1167 18 0.055556 / 1.4111 24 0.041667 / 1.0583
5/8 0.6250 / 15.8750 11 0.090909 / 2.3091 18 0.055556 / 1.4111 24 0.041667 / 1.0583
3/4 0.7500 / 19.0500 10 0.100000 / 2.5400 16 0.062500 / 1.5875 20 0.050000 / 1.2700
7/8 0.8750 / 22.2250 9 0.111111 / 2.8222 14 0.071428 / 1.8143 20 0.050000 / 1.2700
1 1.0000 / 25.4000 8 0.125000 / 3.1750 12/14 0.083333 / 2.1167 20 0.050000 / 1.2700
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