Thread type: Whitworth pipe thread

Whitworth Pipe Threads differ in sealing on the thread (acc. ISO 7/1 and DIN EN 10226) and not sealing on the thread (ISO 228).

The pipe thread types are not easy to understand at first glance. Thanks to our Whitworth pipe thread tables, you can get an overview here. A basic distinction is made between sealing and non-sealing connections. If you use non-sealing connections, you will need an additional sealant to reliably seal your pipe connection. You can easily recognize the differences in a clear table of Whitworth pipe thread types. All Whitworth pipe threads in the table have a flank angle of 55° and the dimensions are given in inches.

In order to create a thread-sealing connection, one of the two threads must be tapered. A mechanical seal is then created when the tapered and cylindrical threads meet. If, on the other hand, both the external and internal threads are cylindrical, the connection will not seal in the thread.

The first Whitworth pipe thread table deals with the G or BSP (British Standard Pipe) thread. This is the most commonly used pipe thread in Germany and you will therefore regularly encounter it in standard applications. This is a non-sealing connection, so both the external and internal threads are cylindrical. In the table for this Whitworth pipe thread, we have given you the outside diameter in inches, but also the corresponding value in mm. This saves you having to do the conversion. In addition to the number of threads per inch, which is standard for inch threads, you will also find the pitch in mm in the Whitworth pipe thread table.

In another Whitworth pipe thread table, you can see the variants for the metal-to-metal sealing connection. The most common case is the combination of cylindrical internal thread Rp and conical external thread R. The conical external thread R with the conical internal thread Rc is used less frequently. The Whitworth thread table for thread-sealing connections also contains the pitch in mm and the number of threads per inch. It also contains values for the outer diameter, flank diameter and core diameter. The Whitworth pipe thread table for sealing connections also contains important information on the tolerances of the thread standards, as these differ from those of the G pipe thread.

Comparison of different Whitworth Pipe Threads 

StandardISO 228 part1ISO 7/1
DIN EN 10226/1
iSO 7/1
DIN EN 10226/2
iSO 7/1
DIN EN 102261+ 2
Kind of ConnectionNon-threaded
sealing connection
Thread tight
end connection
Thread tight-
end connection
Thread tight-
end connection
Internal threadcylindricalcylindricalconical (1:16)Rp or Rc
External threadcylindricalR (conical)R (conical)conical (1:16)


British Standard Pipe DIN ISO 228
Cylindrical Britisch Standard Pipe Thread - not sealing on the thread 

 Major Diameter InchMajor Diameter mmTPIPitch P in mm
G 1/8"0,3839,730280,907
G 1/4"0,51813,160191,337
G 3/8"0,65616,660191,337
G 1/2"0,82520,950141,814
G 5/8"0,90222,910141,814
G 3/4"1,04126,440141,814
G 7/8"1,18930,200141,814
G 1"1,30933,250112,309
G 1 1/8"1,49237,900112,309
G 1 1/4"1,65041,910112,309
G 1 3/8"1,74544,320112,309
G 1 1/2"1,88247,800112,309
G 1 3/4"2,11653,740112,309
G 2"2,34759,610112,309
G 2 1/4"2,58765,710112,309
G 2 1/2"2,96075,180112,309
G 2 3/4"3,21081,530112,309
G 3"3,46087,880112,309
G 3 1/4"3,70093,980112,309
G 3 1/2"3,950100,330112,309
G 3 3/4"4,200106,680112,309
G 4"4,450113,030112,309

Please note:
The Major Diameter of 1" Inch Pipe Thread is 33,25 mm or 1,309 Inches (not 25,4 mm)!
Historically it had it's origin from the manufacture of steel pipes in the beginning of the 20th century. In that time the normal 1" Inch pipes with the internal diameter of 1" Inch had a outside diameter of 1.309 Inches (about 33 mm).

Cross section of a Whitworth pipe thread

The diameter and pitches (Threads per Inch) are all the same in G (BSP), Rp, Rc and R thread.
The differences are G(BSP) is cylindrical and not sealing on the thread, Rp is cylindrical and sealing on the thread. Rc is taper and sealing on the thread. The suitable external thread to Rp and Rc is the R thread.
R Thread is taper and sealing on the thread. Rp, Rc and R differ in tolerances to G (BSP).



d = D
d2 = D2
Minor-Ø d1 = D1Rp / Rc Ra
Tolerance of internal threadTolerance of External thread
1/16280,9077,7237,1426,5611/164± 0,071± 1.1/4± 1± 0,9
1/8280,9079,239,1478,5661/84± 0,071± 1.1/4± 1± 0,9
1/4191,33713,15712,30111,4451/46± 0,104± 1.1/4± 1± 1,3
3/8191,33716,66215,80614,9503/86,4± 0,104± 1.1/4± 1± 1,3
1/2141,81420,95519,79318,6311/28,2± 0,142± 1.1/4± 1± 1,8
3/4141,81426,44125,27924,1173/49,5± 0,142± 1.1/4± 1± 1,8
1112,30933,24931,77030,291110,4± 0,18± 1.1/4± 1± 2,3
1.1/4112,30941,91040,43138,9521.1/412,7± 0,18± 1.1/4± 1± 2,3
1.1/2112,30947,80346,32444,8451.1/212,7± 0,18± 1.1/4± 1± 2,3
2112,30959,61458,13556,656215,9± 0,18± 1.1/4± 1± 2,3
2.1/2112,30975,18473,70572,2262.1/217,5± 0,216± 1.1/2± 1.1/2± 3,5
3112,30987,88486,40584,926320,6± 0,216± 1.1/2± 1.1/2± 3,5
4112,309113,030111,551110,072425,4± 0,216± 1.1/2± 1.1/2± 3,5

Internal Thread Rp (cylindrical) and External Thread R (taper) - sealing on the thread

Cross section of the connection of an internal thread Rp with an external thread R

Internal Thread Rc (taper) and External Thread R (taper) - sealing on the thread

Cross section of the connection of an internal thread Rc with an external thread R