Wire Gauge Chart: AWG and SWG Diameters in mm

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Reviewed by MLC Editorial Team | 18 August 2026

Verified by Rachel Mayfield, Supply Chain Analyst - August 2026

Two wire gauge systems survive in UK workshops: AWG (American Wire Gauge, used for electronics and most modern cable specs) and SWG (British Standard Wire Gauge, BS 3737, still common for older drawings, guitar strings, and traditional trades). They are NOT the same scale - 16 AWG is 1.291 mm but 16 SWG is 1.626 mm - so identify the system before ordering. AWG values below are computed from the defining formula; SWG values are the BS 3737 table.

AWG to mm

AWG	Diameter (in)	Diameter (mm)	Area (mm2)
4/0	0.4600	11.684	107.219
3/0	0.4096	10.405	85.029
2/0	0.3648	9.266	67.431
1/0	0.3249	8.251	53.475
1	0.2893	7.348	42.408
2	0.2576	6.544	33.631
3	0.2294	5.827	26.670
4	0.2043	5.189	21.151
5	0.1819	4.621	16.773
6	0.1620	4.115	13.302
7	0.1443	3.665	10.549
8	0.1285	3.264	8.366
9	0.1144	2.906	6.634
10	0.1019	2.588	5.261
11	0.0907	2.305	4.172
12	0.0808	2.053	3.309
13	0.0720	1.828	2.624
14	0.0641	1.628	2.081
15	0.0571	1.450	1.650
16	0.0508	1.291	1.309
17	0.0453	1.150	1.038
18	0.0403	1.024	0.823
19	0.0359	0.912	0.653
20	0.0320	0.812	0.518
21	0.0285	0.723	0.410
22	0.0253	0.644	0.326
23	0.0226	0.573	0.258
24	0.0201	0.511	0.205
25	0.0179	0.455	0.162
26	0.0159	0.405	0.129
27	0.0142	0.361	0.102
28	0.0126	0.321	0.081
29	0.0113	0.286	0.064
30	0.0100	0.255	0.051

SWG to mm (BS 3737)

SWG	Diameter (mm)	Diameter (in)	Area (mm2)
7/0	12.700	0.5000	126.677
6/0	11.786	0.4640	109.099
5/0	10.973	0.4320	94.567
4/0	10.160	0.4000	81.073
3/0	9.449	0.3720	70.123
2/0	8.839	0.3480	61.362
0	8.229	0.3240	53.184
1	7.620	0.3000	45.604
2	7.010	0.2760	38.595
3	6.401	0.2520	32.180
4	5.893	0.2320	27.275
5	5.385	0.2120	22.775
6	4.877	0.1920	18.681
7	4.470	0.1760	15.693
8	4.064	0.1600	12.972
9	3.658	0.1440	10.509
10	3.251	0.1280	8.301
11	2.946	0.1160	6.816
12	2.642	0.1040	5.482
13	2.337	0.0920	4.290
14	2.032	0.0800	3.243
15	1.829	0.0720	2.627
16	1.626	0.0640	2.076
17	1.422	0.0560	1.588
18	1.219	0.0480	1.167
19	1.016	0.0400	0.811
20	0.914	0.0360	0.656
21	0.813	0.0320	0.519
22	0.711	0.0280	0.397
23	0.610	0.0240	0.292
24	0.559	0.0220	0.245
25	0.508	0.0200	0.203
26	0.457	0.0180	0.164
28	0.376	0.0148	0.111
30	0.315	0.0124	0.078

Telling the two apart

AWG is mathematically defined: each step changes diameter by the 39th root of 92, so 6 gauge steps halve the wire's cross-sectional area. SWG is a lookup table with round-number metric steps in places. If a UK drawing predates the 1970s or covers spring wire, sheet or traditional crafts, suspect SWG. If the spec involves electronics, PCBs or American equipment, it is almost certainly AWG. When in doubt measure the wire: the mm columns above identify the system immediately.

A note on current ratings

This page deliberately gives dimensions only. Safe current-carrying capacity depends on insulation, bundling, ambient temperature and the governing regulations, and must come from the cable manufacturer's data or a qualified electrical design source, not a generic gauge chart.

References

Frequently Asked Questions

What is 16 gauge wire in mm?

It depends on the system: 16 AWG is 1.291 mm diameter, while 16 SWG is 1.626 mm. AWG is the American system used in electronics; SWG is the older British standard. Identify which one your spec uses before ordering.

Are AWG and SWG the same?

No. They are different scales that happen to share the gauge-number format. At gauge 16 the difference is 1.291 mm (AWG) versus 1.626 mm (SWG) - more than 25%. British drawings and traditional trades tend to use SWG; electronics and modern cable specs use AWG.

How is AWG calculated?

AWG is defined by formula: diameter in inches = 0.005 x 92^((36-n)/39), where n is the gauge number. Each 6-gauge step halves the cross-sectional area. SWG has no formula - it is a defined table from BS 3737.

Independent UK engineering trade publication. Company profiles cross-referenced with Companies House.