BWG to mm converter: tube wall thickness
Heat exchanger and stainless tube walls are often specified in BWG; this tool gives the thickness in millimeters.
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How to use it
- Enter bwg number.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Each number has a fixed value in inches in the Birmingham (Stubs) Iron Wire Gauge table; thickness (mm) = inches × 25.4.
Example
Inputs: BWG number = 16. Result: Thickness: 1.651 mm; Thickness in inches: 0.065 in.
Limits and caveats
- BWG values are nominal; the tube standard sets the allowed wall tolerance.
- Hypodermic needle gauge derives from this system, but some nominal needle diameters differ slightly.
Questions about this tool
How thick is 16 BWG in mm?
16 BWG is 0.065 in, which is 1.651 mm.
How thick is 18 BWG?
0.049 in, about 1.245 mm.
Does BWG measure diameter or wall?
For wire it is the diameter; for tubing it gives the wall thickness only, and the outside diameter is stated separately.