Unless you’re a trained electrician, you may not be too familiar with wire gauge, how it is determined, and why it is important. This guide is intended to provide you with that basic understanding.
What is Wire Gauge?
Electrical wire gauge is a number given to an electrical wire to identify how much current it can carry, and to distinguish it from other wires with the same capacity. "American Wire Gauge," also known as AWG, is the name of the standard used throughout North America. Electricians also refer to the gauge of a wire as the “wire size.” So throughout this guide, the terms “wire size,” “AWG,” and “wire gauge” will be used interchangeably.
How is Wire Size Determined?
The AWG of a wire is determined by a cross sectional, diametric measurement of the metal wire itself, not including the thickness of the insulation that envelops it. Electricians use a wire gauge to obtain this measurement. In the AWG naming system, the wire with the lower wire gauge number carries the bigger current. For example, a wire size of 4 carries more current than a wire size of 12. Or think of it this way: thinner wires have higher gauge sizes and carry less current.
But current-carrying capacity is just one of three determinants of wire gauge. Wire gauge also describes the resistance of the wire and its weight per unit of length. So, using micrometers, electricians take into account how much current load the wire is capable of accommodating, as well as the distance it must carry that load, and how much all that wire weighs.
The length of a wire, the wire size (diameter of the solid metal wire), and the distance the current must travel all impact the ability of the current to flow. This resistance on the flow of the current will cause a voltage drop down the line. Also affecting resistance are the type of metal the wire is made of, the load current (in Amps), and other factors.
Why Do Wires of the Same Gauge Sometimes Look Different?
Keep in mind that wire size (AWG) measures the amount of current a solid metal wire can carry, and then correlates it to the diameter of the conductive metal portion of the solid wire. This gets a little wonky when the wire being used is not solid, but consists of smaller, twisted, metal strands. Wire that is made up of strands of much smaller wire takes up a bit more space, so a stranded wire with an AWG of 14 (typically speaker wire) may appear larger than a solid wire with an AWG of 14, but both carry the same amount of current.
Why Using the Proper Wire Gauge is Important
You can put a low current on a thick wire (smaller gauge size), but you shouldn’t attempt to put a high current on a thin wire (larger gauge size). As alluded to earlier, thin wires introduce more resistance, and more resistance in the flow of the current usually means energy loss. For strong, reliable signals, don’t use a wire that is too thin for the current.
Wire Gauge Chart
Electricians typically rely on charts like the one shown here to sort through the myriad considerations, and guide them in selecting the proper wire gauge for the job.
| Wire Size (AWG) | Diameter (MILs) | Area (CM)2 | Feet Per Pound | Ohms Per 1000ft 25°C |
Current Capacity (Amps) |
|---|---|---|---|---|---|
| 4 | 204.3 | 41738.49 | 7.918 | 0.2485 | 59.626 |
| 8 | 128.5 | 16512.25 | 25.24 | 0.7925 | 18.696 |
| 10 | 101.9 | 10383.61 | 31.82 | 0.9987 | 14.834 |
| 12 | 80.8 | 6528.64 | 50.61 | 1.5880 | 9.327 |
| 14 | 64.1 | 4108.81 | 80.39 | 2.5240 | 5.870 |
| 18 | 40.3 | 1624.09 | 203.5 | 6.3860 | 2.320 |
| 20 | 32 | 1024.00 | 222.7 | 10.1280 | 1.463 |
| 22 | 25.3 | 640.09 | 516.3 | 16.2000 | 0.914 |
| 24 | 20.1 | 404.01 | 817.7 | 25.6700 | 0.577 |
| 28 | 12.6 | 158.76 | 2081 | 65.3100 | 0.227 |
| 32 | 8.0 | 64.00 | 5163 | 162.0000 | 0.091 |
| 40 | 3.1 | 9.61 | 34364 |
1079.0000 |
0.014 |
In summary, wire gauge, wire size, and AWG all refer to the same thing. Wire gauge refers to the size of the wire in a rather counterintuitive way: a small wire size designation (a wire gauge of 4, for example) carries big current, while a large wire size (a wire gauge of 37, for example) is intended for the carriage of smaller current. You can put a low current on a smaller wire gauge, but you shouldn’t put a high current on a larger wire gauge.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.