Birmingham Wire Gauge (BWG)
The gauge that Birmingham used, and everyone else had to learn.
Origin
In use in the Birmingham metal trades from the eighteenth century, and never formally legislated. It simply became the standard by weight of production.
The catch
It was never a legal standard, and it never agreed with anyone else’s. A 16-gauge wire from Birmingham was not a 16-gauge wire from Lancashire, and buyers had to specify which town’s gauge they meant. That confusion is precisely what the 1883 Act was passed to end.
| Gauge | Inches | Millimetres | Compare: SWG |
|---|---|---|---|
| 0 | 0.340 | 8.64 | 8.23 mm |
| 4 | 0.238 | 6.05 | 5.89 mm |
| 8 | 0.165 | 4.19 | 4.06 mm |
| 12 | 0.109 | 2.77 | 2.64 mm |
| 16 | 0.065 | 1.65 | 1.63 mm |
| 20 | 0.035 | 0.889 | 0.914 mm |
| 24 | 0.022 | 0.559 | 0.559 mm |
BWG survives today in a specific and slightly unexpected place: steel tubing, particularly for boilers and heat exchangers, is still frequently specified in Birmingham gauge. So a gauge that was never legislated, superseded by statute in 1883, remains in current industrial use nearly a century and a half later. It is also known as the Stubs Iron Wire Gauge, which is the same scale under its maker’s name, and it should not be confused with the Stubs Steel Wire Gauge, which is a different scale entirely.