Wire gauge chart and converter

Convert AWG (also sold as B&S) to mm², kcmil and diameter, and back. Every value is worked out from the AWG formula, not copied from a table.

Convert from

Size given as

Gaugemm²kcmilDiameter

AWG / B&S gauge

1/0 is also written 0, and 2/0 as 00.

Conversion

Copper resistance at 75 °C

6 AWG	13.3 mm²
B&S gauge	6 B&S
Metric size, same or larger	16 mm²
Metric size, next smaller	10 mm²
Area	13.3 mm² · 26,251 cmil
Diameter, solid	4.12 mm · 0.162 in
Resistance	1.61 Ω/km · 0.491 Ω/1000 ft

Choose the size with at least the same area, then check its ampacity in your code book. A size chart does not say how much current a wire may carry.

Check voltage drop on 6 AWG

AWG and B&S wire gauge chart

From 4/0, the largest gauge, to 40 AWG. B&S sizes are the same: 6 B&S is 6 AWG. Values are rounded to 3 significant figures.

Solid wire. Resistance is DC, for copper at 75 °C.
AWG / B&S	Diameter (in)	Diameter (mm)	Area (cmil)	Area (mm²)	Ω per 1000 ft	Ω per km
4/0	0.460	11.7	211,600	107	0.0610	0.200
3/0	0.410	10.4	167,806	85.0	0.0769	0.252
2/0	0.365	9.27	133,077	67.4	0.0969	0.318
1/0	0.325	8.25	105,535	53.5	0.122	0.401
1	0.289	7.35	83,693	42.4	0.154	0.506
2	0.258	6.54	66,371	33.6	0.194	0.638
3	0.229	5.83	52,635	26.7	0.245	0.804
4	0.204	5.19	41,741	21.2	0.309	1.01
5	0.182	4.62	33,102	16.8	0.390	1.28
6	0.162	4.12	26,251	13.3	0.491	1.61
7	0.144	3.66	20,818	10.5	0.620	2.03
8	0.128	3.26	16,510	8.37	0.781	2.56
9	0.114	2.91	13,093	6.63	0.985	3.23
10	0.102	2.59	10,383	5.26	1.24	4.08
11	0.0907	2.30	8,234	4.17	1.57	5.14
12	0.0808	2.05	6,530	3.31	1.98	6.48
13	0.0720	1.83	5,178	2.62	2.49	8.17
14	0.0641	1.63	4,107	2.08	3.14	10.3
15	0.0571	1.45	3,257	1.65	3.96	13.0
16	0.0508	1.29	2,583	1.31	4.99	16.4
17	0.0453	1.15	2,048	1.04	6.30	20.7
18	0.0403	1.02	1,624	0.823	7.94	26.1
19	0.0359	0.912	1,288	0.653	10.0	32.9
20	0.0320	0.812	1,022	0.518	12.6	41.4
21	0.0285	0.723	810	0.410	15.9	52.2
22	0.0253	0.644	642	0.326	20.1	65.9
23	0.0226	0.573	509	0.258	25.3	83.1
24	0.0201	0.511	404	0.205	31.9	105
25	0.0179	0.455	320	0.162	40.3	132
26	0.0159	0.405	254	0.129	50.8	167
27	0.0142	0.361	202	0.102	64.0	210
28	0.0126	0.321	160	0.0810	80.7	265
29	0.0113	0.286	127	0.0642	102	334
30	0.0100	0.255	101	0.0509	128	421
31	0.00893	0.227	79.7	0.0404	162	531
32	0.00795	0.202	63.2	0.0320	204	670
33	0.00708	0.180	50.1	0.0254	257	844
34	0.00630	0.160	39.8	0.0201	325	1,065
35	0.00561	0.143	31.5	0.0160	409	1,343
36	0.00500	0.127	25.0	0.0127	516	1,693
37	0.00445	0.113	19.8	0.0100	651	2,135
38	0.00397	0.101	15.7	0.00797	820	2,692
39	0.00353	0.0897	12.5	0.00632	1,035	3,394
40	0.00314	0.0799	9.89	0.00501	1,305	4,280

mm² to AWG chart

Metric cable is sold in the IEC 60228 sizes. The equivalent gauge is the exact match. To swap a metric cable for a US one, choose the size with at least the same area.

US sizes here are the ones commonly sold: even gauges to 4 AWG, then 3, 2, 1, 1/0 to 4/0 and kcmil. Odd gauges such as 13 AWG exist but are rarely sold.
Metric size	Area (cmil)	Equivalent gauge	US size, same or larger	US size, next smaller
0.5 mm²	987	20.1 AWG	20 AWG	22 AWG
0.75 mm²	1,480	18.4 AWG	18 AWG	20 AWG
1 mm²	1,974	17.2 AWG	16 AWG	18 AWG
1.5 mm²	2,960	15.4 AWG	14 AWG	16 AWG
2.5 mm²	4,934	13.2 AWG	12 AWG	14 AWG
4 mm²	7,894	11.2 AWG	10 AWG	12 AWG
6 mm²	11,841	9.4 AWG	8 AWG	10 AWG
10 mm²	19,735	7.2 AWG	6 AWG	8 AWG
16 mm²	31,576	5.2 AWG	4 AWG	6 AWG
25 mm²	49,338	3.3 AWG	3 AWG	4 AWG
35 mm²	69,073	1.8 AWG	1 AWG	2 AWG
50 mm²	98,676	between 1 and 1/0 AWG	1/0 AWG	1 AWG
70 mm²	138,147	between 2/0 and 3/0 AWG	3/0 AWG	2/0 AWG
95 mm²	187,485	between 3/0 and 4/0 AWG	4/0 AWG	3/0 AWG
120 mm²	236,823	237 kcmil	250 kcmil	4/0 AWG
150 mm²	296,029	296 kcmil	300 kcmil	250 kcmil
185 mm²	365,102	365 kcmil	400 kcmil	350 kcmil
240 mm²	473,646	474 kcmil	500 kcmil	400 kcmil
300 mm²	592,058	592 kcmil	600 kcmil	500 kcmil
400 mm²	789,410	789 kcmil	800 kcmil	750 kcmil
500 mm²	986,763	987 kcmil	1000 kcmil	900 kcmil
630 mm²	1,243,321	1,243 kcmil	1250 kcmil	1000 kcmil
800 mm²	1,578,820	1,579 kcmil	1750 kcmil	1500 kcmil
1000 mm²	1,973,525	1,974 kcmil	2000 kcmil	1750 kcmil

kcmil to mm² chart

Above 4/0, US sizes are given in kcmil, thousands of circular mils: 250 kcmil is 250,000 cmil. The chart gives no diameter for them: cables this large are almost always stranded, and a stranded diameter depends on the stranding.

kcmil	Area (mm²)	Metric size, same or larger	Metric size, next smaller	Ω per km
250 kcmil	127	150 mm²	120 mm²	0.169
300 kcmil	152	185 mm²	150 mm²	0.141
350 kcmil	177	185 mm²	150 mm²	0.121
400 kcmil	203	240 mm²	185 mm²	0.106
500 kcmil	253	300 mm²	240 mm²	0.0846
600 kcmil	304	400 mm²	300 mm²	0.0705
700 kcmil	355	400 mm²	300 mm²	0.0605
750 kcmil	380	400 mm²	300 mm²	0.0564
800 kcmil	405	500 mm²	400 mm²	0.0529
900 kcmil	456	500 mm²	400 mm²	0.0470
1000 kcmil	507	630 mm²	500 mm²	0.0423
1250 kcmil	633	800 mm²	630 mm²	0.0339
1500 kcmil	760	800 mm²	630 mm²	0.0282
1750 kcmil	887	1000 mm²	800 mm²	0.0242
2000 kcmil	1,013	none listed	1000 mm²	0.0212

How the gauge works

AWG is defined by two sizes: 36 AWG is 0.005 in across and 4/0 (0000) is 0.46 in. The 39 steps between them grow by the same ratio, so the diameter of gauge n is:

d = 0.005 in × 92^((36 − n) ÷ 39)

For the aught sizes, n is 0 for 1/0, −1 for 2/0, −2 for 3/0 and −3 for 4/0.
Area in circular mils is the diameter in thousandths of an inch, squared: 12 AWG is 80.8 mils across, so 6,530 cmil. One mm² is 1,973.5 cmil.
Every 3 gauges about doubles the area and halves the resistance. Every 6 gauges about doubles the diameter.

B&S and AWG

B&S stands for Brown & Sharpe, and the B&S gauge is another name for AWG, so the numbers match: 6 B&S is 13.3 mm². In Australia 1/0 is written 0 B&S and 2/0 is 00 B&S. Automotive cable is often sold by a nominal size, such as “6mm” or “6 B&S”, that is not its copper area. Check the real area on the cable or its datasheet, and use that area in the converter.

Solid and stranded wire

The diameters in the chart are for solid wire. A stranded conductor of the same gauge has the same copper area but measures larger, because of the gaps between the strands. To size a stranded wire, read the size printed on the insulation, or measure one strand, find its area in the converter and multiply by the number of strands.

Size, current and voltage drop

Size is not ampacity. How much current a wire may carry depends on its insulation, how it is installed and the wiring code. The ampacity guide explains the check.
Long runs need more. A wire big enough for the current can still drop too much voltage over a long run. Check it with the voltage drop calculator, or the 12V calculator for batteries.
The resistance column uses the copper constant the calculator uses, on a 75 °C basis (see the method page). Cooler copper has less resistance, so a wire at room temperature measures lower.

Frequently asked questions

What is 6 B&S cable in mm²?

6 B&S is the same size as 6 AWG: 13.3 mm² of copper, 4.12 mm across as a solid wire. The nearest metric size with at least as much copper is 16 mm².

Is B&S the same as AWG?

Yes. B&S stands for Brown & Sharpe, and the B&S gauge is another name for the American Wire Gauge, so the numbers are the same. Australian automotive and solar cable is often labelled in B&S, and 0 B&S is 1/0 AWG.

What AWG is 2.5 mm²?

About 13.2 AWG, between 14 AWG (2.08 mm²) and 12 AWG (3.31 mm²). The US size with at least the same area is 12 AWG.

What AWG is 4 mm²?

About 11.2 AWG, between 12 AWG (3.31 mm²) and 10 AWG (5.26 mm²). The US size with at least the same area is 10 AWG.

What is 10 AWG in mm²?

5.26 mm², 2.59 mm across as a solid wire. The nearest metric size with at least as much copper is 6 mm².

Does a bigger gauge number mean a thicker wire?

No, the other way round. In AWG and B&S the number goes down as the wire gets thicker: 10 AWG is thicker than 14 AWG. After 1 AWG come 1/0, 2/0, 3/0 and 4/0, and larger US sizes are given in kcmil.

Does this chart give the current a wire can carry?

No. Ampacity depends on the insulation, how the cable is installed and the wiring code, so it is not a property of the size alone. Check it in the code you work under, such as the NEC, the CEC, BS 7671 or AS/NZS 3008.