Birmingham wire gauge

The steps are irregular. Departmental sanction by the United States government ended in 1914.

Birmingham Wire Gauge
Gauge Diameter in inches
1 2 3 4
0000   0.454    
000   0.425    
00   0.380   0.363
0   0.340   0.331
1   0.300 0.300 0.300
2   0.284 0.280 0.280
3   0.259 0.260 0.260
4   0.238 0.240 0.240
5   0.220 0.220 0.220
6   0.203 0.200 0.200
7   0.180 0.185 0.185
8   0.165 0.170 0.170
9   0.148 0.155 0.155
10   0.134 0.140 0.140
11   0.120 0.125 0.125
12   0.109 0.110 0.110
13   0.095 0.095 0.095
14   0.083 0.085 0.085
15   0.072 0.075 0.075
16   0.065 0.065 0.065
17   0.058 0.058 0.057
18   0.049 0.049 0.050
19   0.042 0.042 0.045
20   0.035   0.040
21   0.032   0.035
22   0.028   0.030
23   0.025    
24   0.022    
25   0.020    
26   0.018    
27   0.016    
28   0.014    
29   0.013    
30   0.012    
31   0.010    
32   0.009    
33   0.008    
34   0.007    
35   0.005    
36   0.004    


1. This column is reserved for a yet-to-be-discovered 18th century list of BWG values.

2. C. Holzapffell.
On the Gauges at present used, for measuring the thickness of sheet metals and wires, and proposals for a new system of Gauges,founded on the decimal subdivision of the Standard Inch.
Journal of the Franklin Institute, vol 15, August, 1847. Page 117
Reprinted from the Glasgow Practical Mechanic and Engineers’ Magazine, circa 1843.

Holzapffel's decimal figures are reprinted, with acknowledgement in, for example,

Joshua Rose.
Modern Machine-Shop Practice, vol 1, 2nd ed.,
New York: Charles Scribner's Sons, 1892. page 384.

and, without acknowledgement, in, for example,

[U.S.] Dept. of Commerce and Labor.
Circular of the Bureau of Standards. No. 31. Copper Wire Tables.
Washington: Government Printing Office, 1912.

Page 35, in a column headed “Birmigham Wire Gauge (Stubs')”, Roebling (source 6 below) also identifies the B.W.G. with Stubs' Iron Wire Gauge, but whatever the situation in the early 1900's, at an earlier date the Birmingham Wire Gauges were not identical with Stubs'. The values given in Roebling's book (page 52) are those of Holtzapffel.

3. Latimer Clark.

4. R. S. Culley.
A Handbook of Practical Telegraphy. 3rd ed. rev and enlarged.
London: Longmans, Green, Reader and Dyer, 1868.
Page 296.

An authoritative source that went through many editions and was adopted by, for example, the Department of Telegraphs for India. But see source note 1, below.



Birmingham Wire Gauge.— The diameters of the several gauges must be considered approximate only. There is no authorised standard, and the sizes of different makers vary considerably.

R. S. Culley.
A Handbook of Practical Telegraphy. 3rd ed. rev and enlarged.
London: Longmans, Green, Reader and Dyer, 1868.
Page 296


1st.— The wire supplied under this tender must be of the gauge known as No. 6, Birmingham Wire Gauge (diameter .170 of an inch.)

Advertisement by Charles T. Chester,
Telegraph Wire.
The Telegrapher, vol 8, no, 21, Jan 13, 1871. Page 166.

The advertisement ran every week, identically worded, so a typographcal error is unlikely. The advertiser, Charles T. Chester, was regarded as one of the two best manufacturers of iron telegraph wire in the United States. Note that in Holtzapffel's list, No. 6 is 0.203 of an inch, not 0.170. Chester appears to be quoting a U.S. government specification.


In purchasing iron wire it has hitherto been the invariable custom to specify its size according to the Birmingham Gauge. This wire gauge varies with every manufacturer, and there is not only no standard from which he can correct his own, but no one is aware on what basis the gauge was originally made, so that it is impossible to reproduce it in any correct shape. Mr. Culley, in a note to table (No. 9) in his hand-book, says, “Birmingham Wire Gauge.—The diameters of the several gauges must be considered approximate only. There is no authorized standard, and the sizes of different makers vary considerably.”

Mr. Latimer Clark's paper, read before the British Association in September, 1867, so well describes the variations of different makers that it is useless to bring forth any further proof of its inconsistency and its self-evident inconvenience. It is evident that, in establishing any gauge, it should have been coherent through out; it should have been based on a regular increasing series, and should have started from some recognized and well known unit. Mr. Latimer Clark has pointed out the probability that the present Birmingham Wire Gauge originated from No. 16 Bell Wire as unit, that wire being 1/16th of an inch in diameter ; but this is a mere arbitrary size to select, and although it may be understood that before telegraphs were in existence bell-hangers would start from a size most convenient to them, that size bears no relation to any telegraphic purpose, and it bears no relation whatever to the remainder of the series.

H. Mallock and W . H. Preece.
On a New Telegraph Wire Gauge.
Telegrapher, vol 8, no 61, 19 October 1871. Page 481.


This gauge (hereinafter referred to as the B. W. G.) is represented by a series of numbered slots or cuts on the edges of a small rectangular steel plate. It is the practice to distinguish the diameters of wires and the thickness of plates of metal by the number of the slot or cut which the wire or plate may fit.

There is no standard of such gauge or common agreement amongst those interested as to what are the dimensions in parts of an inch of the several slots or sizes of the true B. W. G. Its sizes are not geometrically or arithmetically progressive, and, consequently, bear no definite relation to each other. Its origin is obscure, and it would appear that the several slots or sizes arose from time to time as a new wire or new plate was introduced, and as the exigencies of a particular trade demanded. Considerable annoyance to engineers and pecuniary loss to contractors is stated to occur from a want of accuracy in the copies of this gauge, and the necessity of establishing a standard has lately been discussed, both in this country and in the United States.

Board of Trade.
12th Annual Report to Parliament on Standard Weights and Measures, for 1877-78.


When Britain adopted the Imperial Wire Gauge in 1884, the manufacturers of sheet metal rebelled. Though formerly they and the wire makers had used a common gauge, the new gauge suited the needs of wire makers, but not of sheet metal workers. In December the iron manufacturers met and resolved to adopt the Birmingham wire gauge as the standard gauge for sheet metal.

There has been a great deal of discussion among the iron men, and two days ago a very influential meeting was held at the Birmingham Exchange, at which nearly every large sheet-metal works in the district was represented.

It was there stated that the decision arrived at at the meeting in December had not been satisfactory, because manufacturers had not after long aud serious discussion been able to agree since then as to what the Birmingham wire-gauge really has been and is.

The result is a serious dilemma. The new imperial wire-gauge is only adapted for the use of wire-makers, and the old Birmingham gauge is a doubtful, some even said mythical, standard. One party declared it was really Partridge's gauge and another that it was Stubbs's gauge, and the result has been confusion, the meeting unanimously resolved :

That this meeting adopts the gauge known as the Birmingham gauge, aud further resolves that such Birmingham gauge shall be the proposed standard gauge for sheetiron and hoop-iron already printed and issued by the South Staffordshire Ironmasters' Association to the manufactured-iron trade, and by them approved, and also deposited with the Board of Trade, and that such gauge shall in future be used under the initial letters "B. G." This new gauge, to be known hereafter as "B. G.," is described as being a symmetrical adjustment of the Birmingham wire-gauge known as "B. w. g.," formulated by Mr. Hatton at the request of the Iron Masters' Association.

Wilson King, Second Wire Gauge Report. United States Consular Reports. No. 39 — March 1884.
Washington: Department of State. Page 316.


There are several other gauges in use, such as Wynn's, Cocker's, Ryland's, Watkins', Robinson's, and Brown and Sharpe's American gauge, while a great number are also employed under the name of “the old Birmingham wire gauge,” and other titles.

A table attached to Mr. L. Clark's paper gives the diameter of each number of Birmingham wire gauge in decimals of an inch, according to thirteen published lists by different authorities, all of which differ.…

There can be little doubt that reform in this matter is very greatly required. For a long time it has been the custom in specifying the size of the wires for submarine cables to state, besides the number of the Birmingham wire gauge, the decimals of an inch that shall be understood by that number. This has been found necessary on account of the vagueness of the meaning of the words “Birmingham wire gauge,” owing to the number of different interpretations of these words which have grown up through different manufacturers of gauges making them on some arbitrary principle of their own; the principle on which the original B.W.G. was constructed, if it ever had any, having been lost in obscurity possibly by bad workmanship in some of the early gauges.

Review of Report of the Committee of the Society of Telegraph Engineers on the Birmingham Wire Gauge.
Engineering, vol 29, Feb 20 1890. Page 141.


This is abbreviated B. W. G. It is the same as Stubs' Iron Wire Gauge, but entirely different from Stubs' Steel Wire Gauge. Galvanized Telegraph and Telephone Wire, both bare and insulated, and Galvanized Armor Wire are usually designated by this gauge. Its use is not very extensive and is becoming less.

Wire in Electrical Construction.
Trenton, NJ: John A. Roebling's Sons Company, 1916.
Page 51.

for further reading

Thomas Hughes.
The English Wire Gauge, with Descriptive Tables and Drawings.
London: Spon & Co., October, 1879.

Report to the Council of the Society of Telegraph Engineers on the Birmingham Wire Gauge.
Journal of the Society of Telegraph Engineers
, vol 8, pages 476-504, 1879.

A full discussion of the situation. In at least some copies, bound at the end of the volume is a second copy of the report, followed by “On the Unit of the Birmingham Wire Gauge”, by C.V. Walker, a discussion of that paper, and finally Latimer Clark's 1867 paper, “On the Birmingham Wire Gauge”.

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