The Ultimate Guide to Wire Gauge Sizes | Learn What Gauges Are Used For Custom Wire Harness Applications

Different kinds of cables are on wooden pallet.

Wire gauges help determine the effectiveness, as well as the costs of the overall design. That’s why our designers take such care when designing custom wiring harnesses to incorporate the perfect gauges to meet the needs of the project. 

In today’s LiveWire spotlight, we’ll showcase a complete wire gauge guide focused on topics like wire gauge sizes, how to measure wire gauge, and how to choose the right wire gauge in custom cabling applications.

Wire Gauges Explained

First up, what does gauge mean in wire harness design? Wires are produced in a wide variety of widths in order to meet the needs of the project. The diameter of a wire is expressed in a unit known as a gauge, as set by the American Wire Gauge (AWG). The AWG sets corresponding numbers to different diameters of wire gauge. 

Contrary to what you might think, the lower AWG numbers actually correspond to wires with higher diameters and the larger numbers in the AWG wire gauge size chart correspond to smaller diameters of wire. The AWG sets gauges in order to have a unifying system of measure with wires and conductors. It’s important to note that the AWG applies to round, solid, and non-ferrous wires. Non-ferrous metals, like aluminum and copper, make excellent conductors.

Wire diameter is critical in custom wire harness design as it helps to determine how much of an electrical load and the level of resistance, expressed in ohms (Ω). This standardization helps our wire engineers start with materials with known electrical properties to provide the most effective designs possible. In the custom cable manufacturing industry, exactness matters which is why even the smallest degree of error needs to be corrected in a design before ever moving forward with production.  

How to Measure Wire Gauge

To answer questions like, “how thick is 4 gauge wire?”, you need to understand how the AWG wire gauge system works. As we discussed, the larger gauge numbers expressed in an AWG size chart correspond to lower wire diameters and smaller gauge numbers mean larger diameters. 

Before the AWG, different manufacturers had their own unique sizes and systems, making any form of standardization difficult. However, the AWG isn’t the only gauge measurement around with most of the world relying on a metric-based system for gauge measure. For the purpose of this wire gauge guide, we’ll stick with the AWG.

The Formula for Wire Gauge Sizes

Looking at an AWG wire gauge chart, you’ll see 0000 on up to 36 and beyond. A 36 AWG wire is going to be .005 inches while a 0000 AWG is .46 inches. The ratio between these matters is exactly 1 to 92. With 40 different gauge sizes between 0000 and 36, there’s a consistent geometric step with each successive AWG number. 

This is important because it helps to qualify a constant multiple from which the entire system is based. For example, with every 6 gauge of decrease, you’ll get a doubling of the wire’s diameter. Conversely, a 3 gauge decrease doubles the wire’s cross-sectional area. 

Wire Gauge Diameter

The actual formula for figuring out the diameter of wire gauge is a little complicated but one our engineers use in our designs every day to find the perfect wire to match the application. Diameters are calculated with this formula – D(AWG) = 0.005·92((36-AWG)/39) inch. 

For those that want to dig more into the technical side of electronic formulas like this, we recommend a mainstay in the industry known as the “Handbook of Electronics Tables and Formulas” by Howard Sams. 

Wire Resistance & Wire Length

AWG helps to provide consistency to resistance and wire length as well since different gauges will have known levels. The larger a wire’s circumference is, the less resistance the signal or current will have. A very small gauge wire might not be able to handle a given electrical load, which could prove dangerous and even cause a fire. Wire gauges have to be exact in order to create the ideal resistance level in a given custom wire and cable harness. 

Another important consideration is the length of the wire. With longer wires, the signal or current has to simply travel further before reaching a termination. Longer distances lead to more resistance which can degrade the signal. A larger gauge wire can help to make sure that the signal or current is able to travel these long distances without becoming too degraded. In our AWG size chart, you’ll see this expressed as a measure of ohms per 1,000 feet.

You might simply think you should always just use a larger gauge wire and be done but this blanket approach can prove inefficient, especially from a materials-cost perspective. As a custom cable manufacturer, we examine all of the nuances of a design in order to produce the best utilization of our client’s budget, given the parameters of the intended application. This level of sophistication is what truly sets apart working with a custom manufacturer over relying on off-the-shelf cable assemblies.

Wire Gauge Chart

The standardization for diameters and cross-sectional areas presented as AWG sizes is continued to be maintained by the American Society for Testing and Materials (ASTM). The ASTM is actually an international organization that helps to develop consensus across industries for a wide range of technical applications. 

When it comes to the source for an AWG wire gauge chart, the ASTM is the best place to start. For the most up-to-date wire gauge chart see ASTM B258 – 18 Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors. This publication specifies diameters, areas, equations, and rules for calculating AWG sizes. Length of the wire, resistance (Ω), and rated strengths are all required for standardization, as well. As you can imagine, global standardization is difficult and requires developing a complete methodology for the process.

The following wire gauge chart was adapted from an American Wire Gauge reference article published by Boston University:

AWG gaugeDiameter InchesDiameter mmOhms per 1000 ftOhms per kmMax amps for chassis wiringMax amps for power transmission
OOOO0.460011.68400.04900.160720380302
OOO0.409610.403840.06180.202704328239
OO0.36489.265920.07790.255512283190
00.32498.252460.09830.322424245150
10.28937.348220.12390.406392211119
20.25766.543040.15630.51266418194
30.22945.826760.19700.64616015875
40.20435.189220.24850.81508013560
50.18194.620260.31331.02762411847
60.16204.114800.39511.29592810137
70.14433.665220.49821.6340968930
80.12853.263900.62822.0604967324
90.11442.905760.79212.5980886419
100.10192.588260.99893.2763925515
110.09072.303781.26004.1328004712
120.08082.052321.58805.208640419.3
130.07201.828802.00306.569840357.4
140.06411.628142.52508.282000325.9
150.05711.450343.184010.44352284.7
160.05081.290324.016013.17248223.7
170.04531.150625.064016.60992192.9
180.04031.023626.385020.94280162.3
190.03590.911868.051026.40728141.8
200.03200.8128010.15033.29200111.5
210.02850.7239012.80041.9840091.2
220.02540.6451616.14052.9392070.92
230.02260.5740420.3666.780804.70.729
240.02010.5105425.6784.197603.50.577
250.01790.4546632.37106.17362.70.457
260.01590.4038640.81133.85682.20.361
270.01420.3606851.47168.82161.70.288
280.01260.3200464.9212.87201.40.226
290.01130.2870281.83268.40241.20.182
300.01000.254103.2338.49600.860.142
310.00890.22606130.1426.72800.7000.1130
320.00800.2032164.1538.24800.5300.0910
330.007100.18034206.9678.63200.4300.0720
340.006300.16002260.9855.75200.3300.0560
350.005600.14224329.01079.1200.2700.0440
360.005000.12700414.813600.2100.0350

You’ll see in the above chart that amps are listed with each gauge. This is the capacity level that each wire gauge is able to safely handle. Looking at lower gauges and remembering these correspond to thicker wires, you’ll notice that they have higher maximum amp ratings.  

Common Applications of Standard Wire Gauges

Wire gauges will each have their own electrical properties which makes them each perfect for their own unique applications. Higher gauges are great for lighter-duty electrical work, while lower gauges are reserved for more heavy-duty projects. 

The most common gauges of wire out there are 10, 12, and 14 as these are used in building and construction applications. As we’ve seen, when projects require a wire to go a longer distance, the gauge of wire needs to be bumped up in order to compensate and allow electricity and/or signal to pass through it. 

A few of the more common applications with AWG sizes include:

  • 14 Gauge Wire: this is very common in residential wiring applications such as with light fixtures, devices, and household outlets. 
  • 12 Gauge Wire: this is also common for residential wiring to be used for outlets, small appliances, and even smaller air conditioning units.
  • 10 Gauge Wire: 10 gauge is starting to get into larger household appliances such as window air conditioning units, water heaters, and your clothes dryer. 
  • 8 Gauge Wire: this is for larger household appliances such as electric ranges, ovens, and your home’s air conditioning system.
  • 6 Gauge Wire: this is going to be for the largest household appliances and air conditioning units.

Even within a consideration like wire gauges, we see that there is a tremendous level of exactness required from a cable harness design team in order to find the best application. Selecting the best gauge wire for the application takes a lot of careful measurements and considerations during the design phase. Our cable engineers work to find the most efficient means to produce a given assembly within the specifications provided by the client.

Choosing the Perfect Wire Guage

The two most important questions you need to know in your project are wire gauge and wire length. This is determined by looking at what carrying capacity and the level of current, expressed in amps. As we’ve discussed wire gauge is listed based on how the maximum amount of amps that can run through it. Last up is the distance as this is crucial for gauges. You’ll be able to effectively counteract the drop in voltage by increasing the wire gauge, which can handle more amps. 

Getting the Best Design with the Correct Wire Gauge

Working with our client’s unique specifications, the Meridian team is able to consistently exceed our client’s expectations when it comes to delivering the perfect solution for even the most complex issues. Contact our team today to start reviewing your project and to see where utilizing a custom cable manufacturer can benefit your project.