Wire Gauge (AWG) Reference

Quick reference for American Wire Gauge sizes, resistance, and current capacity.

AWG	Diameter (mm)	Area (mm²)	Ω/m	Max current (A)
0	8.251	53.490	3.23e-4	245
1	7.348	42.410	4.07e-4	211
2	6.544	33.630	5.13e-4	181
3	5.827	26.670	6.47e-4	158
4	5.189	21.150	8.15e-4	135
5	4.621	16.770	0.0010	118
6	4.115	13.300	0.0013	101
7	3.665	10.550	0.0016	89
8	3.264	8.366	0.0021	73
9	2.906	6.632	0.0026	64
10	2.588	5.261	0.0033	55
11	2.305	4.172	0.0041	47
12	2.053	3.309	0.0052	41
13	1.828	2.624	0.0066	35
14	1.628	2.081	0.0083	32
15	1.450	1.650	0.0104	28
16	1.291	1.309	0.0132	22
17	1.150	1.038	0.0166	19
18	1.024	0.823	0.0209	16
19	0.912	0.653	0.0264	14
20	0.812	0.518	0.0333	11
21	0.723	0.410	0.0420	9
22	0.644	0.326	0.0530	7
23	0.573	0.258	0.0668	4.7
24	0.511	0.205	0.0843	3.5
25	0.455	0.162	0.1063	2.7
26	0.405	0.129	0.1340	2.2
27	0.361	0.102	0.1690	1.7
28	0.321	0.081	0.2131	1.4
29	0.286	0.064	0.2687	1.2
30	0.255	0.051	0.3389	0.86
32	0.202	0.032	0.5389	0.53
34	0.160	0.020	0.8572	0.32
36	0.127	0.013	1.3610	0.2
38	0.101	0.008	2.1640	0.13
40	0.080	0.005	3.4410	0.09

What is wire gauge calculation?

Wire gauge determines the current-carrying capacity, resistance, and voltage drop of electrical wire. Using wire that is too thin for the current it carries creates a fire hazard — the wire overheats, insulation melts, and fires can result. This calculator helps you select the correct wire gauge (AWG or metric) based on current, distance, and acceptable voltage drop.

The American Wire Gauge (AWG) system assigns numbers to wire sizes — counter-intuitively, smaller numbers mean thicker wire. AWG 14 is thinner than AWG 10. Common household wire is 12 AWG (20A circuits) or 14 AWG (15A circuits). The metric system uses the conductor cross-sectional area in square millimeters, which is more intuitive.

Voltage drop explained

All wire has resistance, and current flowing through resistance creates a voltage drop. Over long distances, this drop can become significant — a 12V system losing 2V to wire resistance means devices only receive 10V. The acceptable voltage drop is typically 3-5% of the source voltage. Longer runs and higher currents require thicker wire.

How to use this tool

Enter the current, wire length (one-way distance — the calculator accounts for the return path), source voltage, and maximum acceptable voltage drop percentage. The tool recommends the minimum wire gauge and shows the actual voltage drop, resistance, and power loss for each AWG size.

Common wire gauges

AWG 18 (0.82 mm2): Small electronics, speakers, low-power lighting. Up to 5A.
AWG 14 (2.08 mm2): Standard 15A household circuits in North America.
AWG 12 (3.31 mm2): Standard 20A household circuits, kitchen and bathroom outlets.
AWG 10 (5.26 mm2): 30A circuits, electric dryers, water heaters.
AWG 6 (13.3 mm2): 60A circuits, electric ranges, subpanels.

Worked example

Run 15 A of 12 V DC to a device 5 metres away using copper. The round-trip conductor length is 10 m. Copper resistance is about 5.2 mΩ per metre for 14 AWG, giving 52 mΩ and a drop of 15 × 0.052 ≈ 0.78 V — over 6%. Stepping up to 10 AWG (about 3.3 mΩ/m) cuts the drop to roughly 0.5 V, under the common 3% target.

Common mistakes

A common mistake is sizing wire only for its ampacity while ignoring voltage drop, which dominates on long low-voltage runs. Another is forgetting that current travels down and back, so both conductors' length must be counted. Bundling cables or high ambient temperatures also lower a wire's safe current, so derating factors from the wiring code must be applied.

Frequently asked questions

Why does distance matter for wire gauge selection?

Wire resistance is proportional to length. A 10-foot run has twice the resistance of a 5-foot run, creating twice the voltage drop. For long-distance runs (like a detached garage or solar panel installation), you often need to use significantly thicker wire than the current alone would require, just to keep voltage drop acceptable.

Is AWG used worldwide?

AWG is primarily used in North America. Most other countries use the metric system with wire sizes specified in square millimeters (mm2). Common metric sizes include 0.75, 1.0, 1.5, 2.5, 4.0, 6.0, 10, and 16 mm2. This calculator converts between AWG and metric so you can work with either system.

Does a lower AWG number mean a thicker wire?

Yes. The American Wire Gauge scale is inverse: as the gauge number falls, the wire gets thicker and carries more current. Each drop of three gauges roughly doubles the cross-sectional area, so 10 AWG has about twice the copper of 13 AWG and far less resistance per metre.