Extension Cords Size Tables

OK, what size cord should you use for which tool? You will have to do a little work to figure this out. It is not hard. Fortunately, many common electrical tools can operate without danger of motor damage when powered by a 16 gauge cord that is 100 feet long. To make sure you are properly protected, use the following sizing guidelines.

All you must do is obtain the motor amperage from the plate on the tool. You will find this information on the small metal plate where the serial number and model number is listed. Usually, you will see an amperage rating. If, for some odd reason, you see watts listed instead of amps, you can convert watts to amps easily! Here is how you do that: The formula for the conversion is simply Voltage x Amps = Watts. Because we use 120 volts as an electrical standard here in the USA, that means that every 600 watts equals 5 amps (120 x 5 = 600). To switch that formula around for people like me who are algebra impaired.

Important Tool Safety Tip: Voltage drop is a reality. Electricity encounters friction as it travels through electrical wires. Knowing this, use only as much extension cord as you really need. In other words, don't use a 100 foot cord for a project that is only 20 feet away. Purchase and maintain an assortment of different length cords.

Multiple tools on one cord - I was guilty of this infraction. On construction sites, we would commonly feed multiple saws and drills from one cord. If the circuit breaker at the panel is working fine, then you will pop the breaker if there is a current overload. However, if the breaker is bad you can either burn up the cord or damage tools from voltage drops. Use common sense.

Sizing an Extension Cord

Step 1

Determine the amperage of the tool(s) being used. Here is a handy list of some common electric power tools. The average amperage is listed below the tool. Always check on your tool label for its specific amperage.

Step 2

Calculate the length of the cord you will need. Of course you want to determine the maximum distance you think you will be from a permanent electrical outlet.

Step 3

Use the following list to select the proper gauge extension cord. Remember, wire gauge refers to the thickness of the actual copper wire. As a wire gets thicker it can carry more electricity (amps). To confuse us, some idiot decided that as a wire gets thicker (bigger) the gauge number should get smaller!

16 Gauge Cords Any 16 gauge cord between 0 and 100 feet long will adequately handle tool loads up to 10 amps.

14 Gauge Cords   Any 14 gauge cord between 0 and 50 feet long will adequately handle loads between 10 and 15 amps.

12 Gauge Cords If your tool load is between 10 and 15 amps and the length of the cord is 50 to 100 feet, you need a 12 gauge cord to safely power any tool.