mm to SWG converter: find the British gauge
Handy when a spec or supplier asks for an SWG number and you have a diameter in millimeters.
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How to use it
- Enter wire diameter.
- 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
The entered diameter is compared with every gauge in the BS 3737 table (inches × 25.4 mm) and the closest one is chosen.
Example
Inputs: Wire diameter = 1.2 mm. Result: Nearest SWG: 18; Diameter of that gauge: 1.2192 mm; Difference: 0.0192 mm.
Limits and caveats
- Measure after removing coating or insulation to get the right gauge.
- If the diameter falls exactly between two gauges, the thicker one is shown.
Questions about this tool
What SWG is 1.2 mm wire?
The nearest is 18 SWG, which is 1.219 mm.
What SWG is 2 mm wire?
The nearest is 14 SWG at 2.032 mm.
Does this work for welding wire?
Yes. Much welding and spring wire is sold by SWG, and diameter is the same basis.