Wire Gauge Current Rating Table: AWG SWG Quick Reference (2026 Practical Guide)

About Standards

There are three commonly used international standards for wire specifications: American (AWG), British (SWG), and Chinese (CWG).

The “square millimeter” rating is a nominal value specified by national standards. Users choose wire gauge based on the load requirements of their electrical cables.

Wire gauge (in square millimeters) is a common term used in electrical installation work. When people say “X square wire,” they’re referring to square millimeters without explicitly stating the unit.

The “square” of a wire actually refers to the cross-sectional area of the wire — the area of the circular cross-section, measured in square millimeters.

Generally speaking, the empirical current capacity is that when the grid voltage is 220V, each square millimeter of wire can carry about 1 kilowatt.

Copper wire can carry 1-1.5 kilowatts per square millimeter, while aluminum wire can carry 0.6-1 kilowatts per square millimeter. Therefore, a 1-kilowatt appliance only needs 1 square millimeter of copper wire.

Specifically for current, during short-distance power transmission, copper wire can generally carry 3A to 5A per square millimeter. Use 5A/sq mm when cooling conditions are good, and 3A/sq mm when they’re not.

Chinese National Standard

According to the national standard “GB/T 4706.1-2005,” we can find the following definitions for qualified conductors:

Appliance Rated Current A	Flexible Cable Cross-section (mm²)	Fixed Wiring Cable Cross-section (mm²)
≤3	0.5 and 0.75	1-2.5
>3 and ≤6	0.75 and 1	1-2.5
>6 and ≤10	1 and 1.5	1-2.5
>10 and ≤16	1.5 and 2.5	1.5-4
>16 and ≤25	2.5 and 4	2.5-6
>25 and ≤32	4 and 6	4-10
>32 and ≤40	6 and 10	6-16
>40 and ≤63	10 and 16	10-25

Stranded Wire Cross-section Calculation

Knowing the wire gauge (in square millimeters), calculate the wire radius using the circle area formula:

Wire gauge (mm²) = π (3.14) × wire radius (mm)²

Knowing the wire gauge, calculating wire diameter works the same way. For example:

The wire diameter of 2.5 sq mm wire is: 2.5 ÷ 3.14 = 0.8, then take the square root to get 0.9 mm. Therefore, the wire diameter of 2.5 sq mm wire is: 2 × 0.9 mm = 1.8 mm.

Knowing the wire diameter, calculating wire gauge also uses the circle area formula:

Wire gauge = π (3.14) × wire diameter² / 4

Cable sizes are also labeled in square millimeters. For stranded wire, it’s the sum of the cross-sectional areas of each conductor.

Cable cross-section calculation formula:

0.7854 × wire radius (mm)² × number of strands

For example, 48 strands (each strand radius 0.2 mm) 1.5 sq mm wire:

0.785 × (0.2 × 0.2) × 48 = 1.5 sq mm

American Wire Gauge AWG

The American Wire Gauge (AWG) size and characteristics chart lists the AWG dimensions of cables/conductors. In addition to wire size, the table provides values for load (current) carrying capacity, resistance, and skin effect.

Current Carrying Capacity

Definition: Current carrying capacity is the wire’s ability to carry current. In other words, how many amperes can it transmit? The table below is a guide for load current or copper wire current carrying capacity, following the American Wire Gauge spreadsheet and formula handbook. As you might guess, the rated current capacity is just a rule of thumb. In careful engineering design, voltage drop, insulation temperature limits, thickness, thermal conductivity, air convection, and temperature should all be considered. The maximum amperage for power transmission uses the rule of 700 circular mils per amp, which is very, very conservative. The maximum amperage for chassis wiring is also a conservative rating, but it applies to wiring in air, not bundled. For shorter wires, such as those used for battery packs, you should weigh resistance and load against size, weight, and flexibility.

100% Skin Depth Maximum Frequency

This data is useful for high-frequency AC engineering. When conducting high-frequency AC through a wire, current tends to flow along the outer surface of the wire. This increases effective resistance. The frequencies listed in the table show the calculated skin depth equal to the wire radius, indicating that above this frequency, you should start considering skin effect when calculating wire resistance.

Reference Table (Copper Wire)

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AWG	Diameter	Diameter [inches]	Area	Resistance [Ω/km]	Resistance [Ω/kilo-inch]	Power Transfer Max Current [Amps]	Chassis Wiring Max Current [Amps]	Max Frequency 100% Skin Depth	Breaking Force
40	0.07874	0.0031	0.00501	3440	1049	0.0137	0.09	2900kHz	0.132
39	0.0889	0.0035	0.00632	2728	831.8	0.0175	0.11	2250kHz	0.163
38	0.1016	0.004	0.00797	2163	659.6	0.0228	0.13	1750kHz	0.204
37	0.1143	0.0045	0.01	1715	523.1	0.0289	0.17	1350kHz	0.259
36	0.127	0.005	0.0127	1360	414.8	0.035	0.21	1100kHz	0.327
35	0.14224	0.0056	0.016	1079.12	329	0.044	0.27	870kHz	0.417
34	0.16002	0.0063	0.0201	855.752	260.9	0.056	0.33	690kHz	0.499
33	0.18034	0.0071	0.0254	678.632	206.9	0.072	0.43	540kHz	0.590
32	0.2032	0.008	0.032	538.248	164.1	0.091	0.53	430kHz	0.816
31	0.22606	0.0089	0.0404	426.728	130.1	0.113	0.7	340kHz	1.021
30	0.254	0.01	0.0509	338.496	103.2	0.142	0.86	270kHz	1.247
29	0.28702	0.0113	0.0642	268.4024	81.83	0.182	1.2	210kHz	1.633
28	0.32004	0.0126	0.081	212.872	64.9	0.226	1.4	170kHz	2.041
27	0.36068	0.0142	0.102	168.8216	51.47	0.288	1.7	130kHz	2.495
26	0.40386	0.0159	0.129	133.8568	40.81	0.361	2.2	107kHz	3.266
25	0.45466	0.0179	0.162	106.1736	32.37	0.457	2.7	85kHz	4.082
24	0.51054	0.0201	0.205	84.1976	25.67	0.577	3.5	68kHz	5.216
23	0.57404	0.0226	0.258	66.7808	20.36	0.729	4.7	53kHz	6.577
22	0.64516	0.0254	0.326	52.9392	16.14	0.92	7	42kHz	8.165
21	0.7239	0.0285	0.41	41.984	12.8	1.2	9	33 kHz	10.433
20	0.8128	0.032	0.518	33.292	10.15	1.5	11	27 kHz	13.154
19	0.91186	0.0359	0.653	26.40728	8.051	1.8	14	21kHz	16.783
18	1.02362	0.0403	0.823	20.9428	6.385	2.3	16	17kHz	21.319
17	1.15062	0.0453	1.04	16.60992	5.064	2.9	19	13 k Hz	26.762
16	1.29032	0.0508	1.31	13.17248	4.016	3.7	22	11 k Hz	34.019
15	1.45034	0.0571	1.65	10.44352	3.184	4.7	28	8250Hz	42.638
14	1.62814	0.0641	2.08	8.282	2.525	5.9	32	6700Hz	53.977
13	1.8288	0.072	2.62	6.56984	2.003	7.4	35	5300Hz	68.039
12	2.05232	0.0808	3.31	5.20864	1.588	9.3	41	4150Hz	89.358
11	2.30378	0.0907	4.17	4.1328	1.26	12	47	3200Hz	112.945
10	2.58826	0.1019	5.26	3.276392	0.9989	15	55	2600Hz	142.428
9	2.90576	0.1144	6.63	2.598088	0.7921	19	64	2050Hz	172.365
8	3.2639	0.1285	8.37	2.060496	0.6282	24	73	1650Hz	217.724
7	3.66522	0.1443	10.5	1.634096	0.4982	30	89	1300Hz	274.423
6	4.1148	0.162	13.3	1.295928	0.3951	37	101	1100Hz	344.730
5	4.62026	0.1819	16.8	1.027624	0.3133	47	118	810Hz	435.449
4	5.18922	0.2043	21.2	0.81508	0.2485	60	135	650Hz	548.847
3	5.82676	0.2294	26.7	0.64616	0.197	75	158	500Hz	693.996
2	6.54304	0.2576	33.6	0.512664	0.1563	94	181	410Hz	875.433
1	7.34822	0.2893	42.4	0.406392	0.1239	119	211	325Hz	1102.229
0(1/0)	8.25246	0.3249	53.5	0.322424	0.0983	150	245	250Hz	1387.993
00(2/0)	9.26592	0.3648	67.4	0.255512	0.0779	190	283	200Hz	1750.867
000(3/0)	10.40384	0.4096	85	0.202704	0.0618	239	328	160Hz	2204.459
0000(4/0)	11.684	0.46	107	0.16072	0.049	302	380	125Hz	2775.985

References:

1. NEC (National Electrical Code) Table 310-16 Wire Ampacity Standard

2. IEC 60287 Cable Ampacity Calculation Standard