AWG (American Wire Gauge)

1. What is AWG?

AWG (American Wire Gauge) is a standardized wire gauge system used predominantly in North America and throughout the global electronics industry to specify the diameter of round, solid, nonferrous electrically conducting wires.

Unlike the JIS standard, which categorizes wires by their cross-sectional area in "SQ" (mm^2), the AWG system is based on the wire diameter. Because the gauge numbers originate from the number of drawing operations required to produce a given wire size, the smaller the AWG number, the thicker the wire (and the higher its current capacity), while the larger the number, the thinner the wire.

When selecting wiring to connect a power supply to a load, choosing the appropriate AWG size is essential not only to ensure sufficient current capacity but also to minimize voltage drop (voltage loss across the wiring length).

2. AWG-to-SQ Metric Conversion and Current Capacity Table

The following table serves as a general guide for AWG sizes, their approximate metric equivalents (SQ), and electrical specifications for typical equipment wiring.

AWG(Gauge)	Conductor Diameter(mm)	Cross-Sectional Area(mm²)	Approximate JIS Value(SQ)	Conductor Resistance(Ω/km at 20°C)	Reference Ampacity(A) *1
0000	0.4600	11.6840	107	0.1607	302
000	0.4096	10.4038	85.0	0.2027	239
00	0.3648	9.2659	67.4	0.2555	190
0	0.3249	8.2525	53.5	0.3224	150
1	0.2893	7.3482	42.4	0.4064	119
2	0.2576	6.5430	33.6	0.5127	94
3	0.2294	5.8268	26.7	0.6462	75
4	0.2043	5.1892	21.1	0.8151	60
5	0.1819	4.6203	16.8	1.0276	47
6	0.1620	4.1148	13.3	1.2959	37
7	0.1443	3.6652	10.6	1.6341	30
8	0.1285	3.2639	8.37	2.0605	24
9	0.1144	2.9058	6.63	2.5981	19
10	0.1019	2.5883	5.26	3.2764	15
11	0.0907	2.3038	4.17	4.1328	12
12	0.0808	2.0523	3.31	5.2086	9.3
13	0.0720	1.8288	2.63	6.5698	7.4
14	0.0641	1.6281	2.08	8.2820	5.9
15	0.0571	1.4503	1.65	10.4435	4.7
16	0.0508	1.2903	1.31	13.1725	3.7
17	0.0453	1.1506	1.04	16.6099	2.9
18	0.0403	1.0236	0.823	20.9428	2.3
19	0.0359	0.9119	0.653	26.4073	1.8
20	0.0320	0.8128	0.519	33.2920	1.5
21	0.0285	0.7239	0.412	41.9840	1.2
22	0.0253	0.6426	0.325	52.9392	0.92
23	0.0226	0.5740	0.259	66.7808	0.729
24	0.0201	0.5105	0.205	84.1976	0.577
25	0.0179	0.4547	0.162	106.1736	0.457
26	0.0159	0.4039	0.128	133.8568	0.361
27	0.0142	0.3607	0.102	168.8216	0.288
28	0.0126	0.3200	0.08	212.8720	0.226
29	0.0113	0.2870	0.0647	268.4024	0.182
30	0.0100	0.2540	0.0507	338.4960	0.142
31	0.0089	0.2261	0.0401	426.7280	0.113
32	0.0080	0.2032	0.0324	538.2480	0.091
33	0.0071	0.1803	0.0255	678.6320	0.072
34	0.0063	0.1600	0.0201	855.7520	0.056
35	0.0056	0.1422	0.0159	1079.1200	0.044
36	0.0050	0.1270	0.0127	1360.0000	0.035
37	0.0044	0.1143	0.0103	1715.0000	0.0289
38	0.0040	0.1016	0.00811	2163.0000	0.0228
39	0.0035	0.0889	0.00621	2728.0000	0.0175
40	0.0031	0.0787	0.00487	3440.0000	0.0137

*1 Conditions for Reference Ampacity:

The ampacity values listed above are calculated for standard single-conductor vinyl equipment wire (maximum conductor temperature of 105°C) in free air at an ambient temperature of 30°C. For actual installation environments-taking ambient temperature and wire bundling into account-apply the correction factors described below to calculate the safe allowable current. For long-distance wiring, consider selecting a wire one size larger to account for voltage drop (losses caused by loop resistance).

3. Difference Between Solid and Stranded Wires

Even with the same AWG number, wire conductors are available in two types of structures: "Solid" and "Stranded." Each has distinct applications.

Solid Wire:
Consists of a single, thick strand of copper. It offers stable electrical characteristics and is ideal for permanent, fixed connections such as terminal blocks or PCBs. However, it is rigid, making it prone to metal fatigue and breakage under repeated bending or in moving parts.
Stranded Wire:
Composed of multiple thin strands twisted together to form a single conductor. It is highly flexible and easy to route, making it the preferred choice for internal wiring within power supplies and locations subjected to frequent bending or vibration.

Practical Tip:

Because stranded wire contains microscopic gaps between the individual strands, its overall finished outer diameter (O.D.) is slightly larger than that of a solid wire with the same AWG number. When selecting routing holes, connectors, or crimp terminals, always check the wire's actual overall outer diameter rather than relying solely on the conductor cross-sectional area (mm²).

4. Correction Factors for Ambient Temperature and Bundling (Derating)

As current flows through a wire, electrical resistance generates heat. When wires are routed in high-temperature environments or tightly bundled together (multiple bundled conductors), heat dissipates poorly, increasing the risk of insulation degradation or melting.

Therefore, in actual system design, the reference ampacity must be derated by multiplying it by the following "Current Reduction Factors."

① Ambient Temperature Correction Factor (Kt)

When the ambient temperature exceeds 30°C, apply the following correction factors to reduce the allowable current (based on a 105°C heat-resistant wire standard).

Ambient Temperature	30°C or below	40°C	50°C	60°C
Correction Factor	1.00	0.93	0.85	0.77

② Bundling Factor / Cable Bundling Reduction Factor (Kn)

When multiple wires are bundled together with zip ties or routed together inside the same conduit or duct, apply the following reduction factors based on the number of conductors.

Number of Bundled Wires	1 (Single wire)	2 to 3	4	5 to 6
Reduction Factor	1.00	0.70	0.63	0.56

Calculation Example:: When using an AWG18 wire (Reference Ampacity: 15.0A) in an environment with an "ambient temperature of 50°C" and "bundled with 3 wires total": Actual Ampacity = 15.0 A x 0.85 (Temperature Factor) x 0.70 (Bundling Factor) = 8.925 A Consequently, the maximum allowable current under these specific conditions is derated to 8.9A. Always incorporate this derating process into your power system designs to ensure safety and reliability.

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