Manufacturers do not publish amperage and gauge charts for their extension cords. They usually ignore the concept because they expect contractors and laypeople to use conventional wire-size charts to make decisions. For instance:
Extension Cord Amperage Chart
| Gauge | Amps (Temperature 75˚C) |
| 6 AWG | 65 AMPS |
| 8 AWG | 55 AMPS |
| 10 AWG | 35 AMPS |
| 12 AWG | 25 AMPS |
| 14 AWG | 20 AMPS |
| 16 AWG | 17 AMPS |
| 18 AWG | 14 AMPS |
| 20 AWG | 11 AMPS |
The amps are self-explanatory. They show the amount of electricity flowing through a circuit or appliance. You need to know the amps because they will tell you whether or not a cable can withstand an application’s electrical requirements.
If you don’t know the gauge and amps, you may connect a machine that uses too much power, overwhelming the extension cord and starting a fire. Knowing the gauge and amps makes you less likely to overload the extension cord.
The gauge goes hand in hand with the amps because it reveals the thickness.
Some contractors have created charts that classify extension cords according to their ampacity. For instance:
| 16 AWG | Light Duty | 13 A – 10A |
| 14 AWG | Medium Duty | 15A – 13A |
| 10 AWG | Heavy Duty | 15A+ |
Many contractors confuse laypeople by using terms like ‘Heavy-Duty’ and ‘Light-Duty.’ Tables like the one above provide clarification by assigning an amp rating to each category. This allows laypeople to understand better what each classification means.
You will also find detailed tables that associate each gauge with examples of the devices it can run as opposed to creating ambiguous categories. For instance:
| 18 AWG | Jig Saw, Drill, Detail Sander |
| 16 AWG | Belt Sander, Reciprocating Saw |
| 14 AWG | Miter Saw, Router |
| 12 AWG | Radial Arm Saw |
The table above gives you an idea of the appliances each gauge can run. However, you don’t need this chart to select the correct extension cord. A standard wire size chart is still the best option because it provides vital details that shape your decision.
That includes temperature, wire type, and material. Admittedly, most laypeople can select the right extension cord without considering these additional variables.
The most important consideration is the ampacity because it determines whether the extension cord will overload and start a fire or run your application safely and without incident. Most consumers use the following steps to select an extension cord:
- Identify the devices you want to run.
- Use the label to find the wattage of each appliance.
- Turn the watts into amps. If you expect the extension cord to support multiple devices, get their total amperage.
- Compare the total amps to a wire size chart to get the gauge.
You can reverse the process by finding the gauge of an extension cord you already own, using the gauge to find the amps in a wire size chart, and comparing the results to the total amps of your devices.
You should only use an extension cord whose amp rating exceeds the ampacity of the appliance.
Variables like the temperature and material can finetune your selection, especially if you intend to deploy the extension cord in rugged locations with potentially dangerous conditions.
Things To Consider While Choosing Different Gauge Extension Cord With Respect To Its Amps
Temperature
Look at the wire ampacity size chart. It shows the ampacity of each gauge at 60, 70, and 90 degrees C. A 14-gauge wire can transmit 20 amps at 60 degrees C, but that figure jumps to25 amps at 90 degrees C.
Why? Because the ampacity increases with the temperature. This makes sense once you realize that a wire’s gauge shows you the number of amps it can carry without overheating. Every decision you make regarding electrical wiring is designed to transmit electricity without starting a fire.
Overheating is an ever-present threat because electricity generates heat when it flows through a conductor. You can blame this phenomenon on the resistance found in every conductor. Therefore, you must identify the amount of power an electrical line can withstand without melting.
An increase in the temperature will force you to reduce the current. You see this when a contractor buries a cable behind a wall. They will restrict the line to small loads to reduce the chances of overheating.
Even though the cable can withstand more power under normal circumstances, the absence of proper ventilation will force you to limit the load size. Contractors apply similar precautions in settings with a high ambient temperature.
The reverse is also true. A wire with a higher temperature rating can survive in settings with a significant ambient temperature without overheating. Therefore, you can afford to burden it with more electricity.
The temperature rarely enters discussions because the variable doesn’t matter to most laypeople. You don’t need to know the temperature rating of the extension cord in your bedroom. The temperature is more likely to influence a contractor’s selection of a commercial-grade extension cord in an industrial setting, especially if they intend to expose the cable to high ambient temperatures.
However, laypeople can still account for the temperature because it affects the extension cord’s ampacity. You can select a line with a higher temperature rating because it can transmit more power without overheating.
Using the example above, you may target 14AWG wiring with a 90-degree temperature rating because it can tolerate 25 amps as opposed to the 20 amps you find at the 60-degree temperature rating.
Distance
The distance has a stronger impact on your selection than the temperature because extension cords bridge the gap between outlets and appliances. You buy these devices because you want to run your equipment, but the power cord is too short to reach the outlet.
Unfortunately, people tend to buy the longest extension cords they can find because of the flexibility it gives them. They can operate appliances both near and far. But that flexibility has a price. Long extension cords are more likely to overheat because of the significant resistance they bring to the table.
If you increase the distance an extension cord must cover, you must reduce the amps. Why? Because fewer amps generate less heat. Reducing the distance lowers the length, which, in turn, elevates the amps you can transmit.
If you can’t reduce the length because of the considerable distance you need to cover, get a thicker conductor. A larger gauge can counter the resistance and voltage drop in a long cable.
Load
This goes without saying. The load will dictate the gauge and amps. A larger load transmits more amps. Therefore, it needs thicker wiring. A smaller load can utilize a lower gauge without overheating.
What do you want to run? Find the wattage of the appliance and turn the unit into amps. Use the equipment’s amps to find the gauge in a wire size chart. Don’t hesitate to plug a heavy-duty appliance into a wall outlet when the opportunity arises. The wall outlet is still the safest option.
Price
Contractors will discourage you from using the price to make decisions. After all, many consumers start fires by trying to cut costs. They buy cheap extension cords with questionable origins that can’t withstand the strain of running medium or heavy-duty appliances.
However, the price still matters because it determines what you can afford. There’s no point in setting your sites on a 10AWG extension cord if you don’t have the money to buy it. And unfortunately, even though thicker gauges are safer because they can transmit a lot of power without overheating, they are significantly more expensive.
Limit your options to gauges that fit within your budget. Don’t try to save money by buying cheaper, shorter cables and daisy-chaining them. You will start a fire.
How Many Appliances Do You Want The Extension Cord To Run?
Some extension cords have one socket. Others have multiple sockets. Make sure the extension cord’s ampacity and gauge can withstand the combined load of all the devices you want to operate.
If you can’t afford an extension cord strong enough to accommodate multiple appliances, stick with a lower gauge but run the appliances one at a time. Don’t use them simultaneously. Otherwise, you will overload the extension cord.