Inch threads include Whitworth threads and Unified Standard threads.
Whitworth threads are the standard threads used for British inch fasteners, with a thread angle of 55 degrees. They are normally represented by the nominal diameter (in inches) and the number of wires per inch, using the symbol “”. For example, 1/2″-12BSW represents a coarse Whitworth thread with a nominal diameter of 1/2 inch.
Unified Standard threads are the standard threads used for American inch fasteners, with a 60 degree thread angle. They are generally represented by a code (for nominal diameters less than 1/4 inch) or the fraction of the nominal diameter in inches (for diameters greater than or equal to 1/4 inch), the number of threads per inch and a designation ( UNC, UNF). For example, 1/2″-13UNC represents a coarse unitized standard thread with a nominal diameter of 1/2 inch.
Nominal diameters and threads per inch of Whitworth threads and Unified Standard threads:
| Main thread diameter | ANSI B1.1-182 Unified Standard Thread | Whitworth Line BS84-1956 | ||||
| Inch | Size code | Thick Yarn UNC |
Fine Thread UNF |
Size code | Thick Yarn B.S.W. |
Fine Thread BSF |
| 0.0600 | 0# | 80 | ||||
| 0.0625 | 01/16 | 60 | ||||
| 0.0730 | 1# | 64 | 72 | |||
| 0.0860 | two# | 56 | 64 | |||
| 0.0938 | 03/32 | 48 | ||||
| 0.0990 | 3# | 48 | 56 | |||
| 0.1120 | 4# | 40 | 48 | |||
| 0.1250 | 5# | 40 | 44 | 1/8 | 40 | |
| 0.1380 | 6# | 32 | 40 | |||
| 0.1563 | 05/32 | 32 | ||||
| 0.1640 | 8# | 32 | 36 | |||
| 0.1875 | 03/16 | 24 | 32 | |||
| 0.1900 | 10# | 24 | 32 | |||
| 0.2160 | 12# | 24 | 28 | |||
| 0.2189 | 07/32 | 24 | 28 | |||
| 0.2500 | 1/4 | 20 | 28 | 1/4 | 20 | 26 |
| 0.2812 | 09/32 | 26 | ||||
| 0.3125 | 05/16 | 18 | 24 | 05/16 | 18 | 22 |
| 0.3750 | 3/8 | 16 | 24 | 3/8 | 16 | 20 |
| 0.4375 | 7/16 | 14 | 20 | 7/16 | 14 | 18 |
| 0.5000 | 1/2 | 13 | 20 | 1/2 | 12 | 16 |
| 0.5625 | 16/09 | 12 | 18 | 16/09 | 12 | 16 |
| 0.6250 | 5/8 | 11 | 18 | 5/8 | 11 | 14 |
| 0.6875 | 11/16 | 11 | 14 | |||
| 0.7500 | 3/4 | 10 | 16 | 3/4 | 10 | 12 |
| 0.8125 | 13/16 | 12 | ||||
| 0.8750 | 7/8 | 9 | 14 | 7/8 | 9 | 11 |
| 1.0000 | 1 | 8 | 12 | 1 | 8 | 10 |
| 1.1250 | 1-1/8 | 7 | 12 | 1-1/8 | 7 | 9 |
| 1.2500 | 1-1/4 | 7 | 12 | 1-1/4 | 7 | 9 |
| 1.3750 | 1-3/8 | 6 | 12 | 1-3/8 | 8 | |
| 1.5000 | 1-1/2 | 6 | 12 | 1-1/2 | 6 | 8 |
| 1.6250 | 1-5/8 | 1-5/8 | 8 | |||
| 1.7500 | 1-3/4 | 5 | 1-3/4 | 5 | 7 | |
| 2,0000 | two | 4.5 | two | 4.5 | 7 | |
| 2.2500 | 2-1/4 | 4.5 | ||||
| 2.5000 | 2-1/2 | 4 | ||||
| 2.7500 | 2-3/4 | 4 | ||||
| 3.0000 | 3 | 4 | ||||
| 3.2500 | 3-1/4 | 4 | ||||
| 3.5000 | 3-1/2 | 4 | ||||
| 3.7500 | 3-3/4 | 4 | ||||
| 4.0000 | 4 | 4 | ||||
