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Extension Cords Size Chart

Extension Cord Sizing TIPS

OK, what size cord should you use for which tool? It's not hard to figure out - See Below.

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're properly protected, use the following sizing guidelines below.

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. A tool may say it's rated for 8 amps. That's amperage.

Ohms Law

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:

Voltage x Amps = Watts

120 x 20 = 2,400

120 x 15 = 1,800

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).

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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 1 Cord?

I was guilty of this infraction many years ago before I fully understood all that's involved.

On construction sites, we'd commonly feed multiple saws and drills from one cord. If the circuit breaker at the panel is working fine, then you'll pop the breaker if there's a current overload.

But, if you've got a smaller-gauge extension cord, it's possible to overheat the cord and melt the insulation before the circuit breaker would trip!

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.

Here are some COMMON amperage ratings of tools around your home:

  • Circular saw: 12-15 amps
  • Power drill: 3-7 amps
  • Hedge Trimmer: 2-3 amps
  • Weed Wacker: 2-4 amps
  • Electric Chain Saw: 7-12 amps
  • Leaf Blower: 6-12 amps
  • Electric Lawn Mower: 6-12 amps
  • Table Saw: 14-20 amps!
  • Reciprocating Saw: 6-8 amps
  • Router: 4-6 amps

 

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!

Here's what I mean. A 14-gauge wire can handle LESS current than a 12-gauge wire. The number 14 is bigger than 12. Confused? You should be!

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.

CAUTION: Most circuits in ordinary houses are wired with 14-gauge solid copper wire. This means in the circuit breaker panel you'll see a 15-amp breaker. You may purchase a 12-gauge extension cord thinking that you'll be able to operate a powerful table saw but the breaker will probably trip when you load the saw. Remember, the circuit is rated for the SMALLEST SIZED cable or wire in the circuit.

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Then add to that the fact that other things, like a garage light, or some other appliance could be on the same circuit you've plugged the extension cord into. This adds to the total load on the circuit! You may think you have 15 amps available going to your extension cord, but several of those amps might be in use from something else.

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18 Responses to Extension Cords Size Chart

  1. I really appreciated your website info regarding what size extension cord I might need. Could you give me your opinion.

    I have a Taylor soft serve Ice cream machine (Refrigeration basically off and on) that will be used at wedding receptions and out doors. Ideally I wanted to get a 100 foot extension cord.

    The machine states its 16 amps at 110 v and requires a dedicated 20 amp circuit/outlet and the cord coming out of machine states 12/3 300volts.

    I was hoping maybe a 10/3 size extension cord at 100 feet would provide up to and maintain 20 amps by the time you hit the 100 feet, but not so sure. Would I need to go with an 8/3 to have at least 20 amps available at 100 feet with current drop, I would think that the 8/3 for sure would maintain up to 20 amps but cannot find anything beyond a 50 foot in the 8/3 size but have found the 10/3 in the 100 foot range everywhere.

    What do you think between the 8/3 and 10/3 for maintaining 20 amps at 100 feet. I appreciate any opinions or math formula's used to figure this out. I figure if machine is 16 amps then giving the extra up to 20 is most likely the way to go, I guess.

    Thanks much

    Best regards

    Tiffany

    • The 10/3 will be more than enough. A 12 gauge wire is rated for 20 amps.

      The problem you'll have at other venues is the LACK of a dedicated circuit that you plug your extension cord into.

      But it gets worse. If you're at a residential home, MOST branch circuits are typically fed with 14-gauge wire rated for only 15 amps.

      Your cord may be able to handle the load, but it's what's between the extension cord and the service panel that counts.

  2. I want to run two 100-ft extension cords connected together to power two table lamps (60watt lamps) in my makeshift bunkhouse at my camping area. First, is this safe to do? And second, if it is, what gage wire extension cords should I purchase. Thanks.

    • can two 100ft. be jointed to make the 200 ft. with a 12/3 gauge extension cord supply a 12 amp electric
      push mower? will it damage the motor with that connection by losing too much voltage.

    • The current rating is based on the size and length of the cord. There is no perfect conductor, so even solid copper wire creates resistance (ohms). The smaller the conductor and the longer the wire, the more the resistance and therefore the less current the cord can handle. A 100' 12 ga. cord connected to a second 100' 12 ga. cord is going to allow less current (amps) than a single 100' 12 ga. cord. That is actually what I was searching when I came across this site--the allowable current with subsequent lengths. Also, if you are mixing cord gauges, use the heaviest gauge (smallest number) closest to the receptacle. Thus, if you have a 12 ga., 14 ga. and a 16 ga. cord that you are using, plug the 12 ga. cord into the outlet, the 14 ga. cord into the 12 ga. and the 16 ga. cord will be providing power to the appliance.

  3. If you use cfl or led bulbs that are 60 watt equivalents their actual wattage will be closer to 11 to 13 watts each, making for a total of about 25 watts.Assuming the voltage at the outlet is a normal 115 to 120 volts then you will only be using about a quarter of an amp which is next to nothing. As long as your extension cords are approved for outdoor usage your typical 16 gauge should be more than enough.

  4. I have an above ground pool that runs on an extension cord. I had a dedicated outlet run from the breaker box exclusively for this purpose. I originally used a100' 12 gauge with no problems. A couple of seasons ago I switched to a 50' + a 25' 12gauge for ease of disconnecting. It's there aa problem going this because I went to plug it in today & saw a puff of smoke??? Yes, I immediately unplugged it.

  5. What happens if I use a 16 gauge instead of a 14 gauge 100' for 12 amp electric lawnmower? Home Depot is pushing the 14 gauge.
    I used the 16 gauge 100' for a 13.5 amp snow blower last year. Home Depot recommended the 16 gauge.
    The 16 gauge worked perfectly for the 13.5 amp at 100 ft..
    It should make no difference, or maybe it does, but the house and all the breakers, and the outlet used, were all professionally upgraded before using the snow blower.

  6. I have a new pool pump that has a dial for backwash,rinse,and regular with pump. How do I know what Guage extension cord to use

  7. What if you want to run 2 items off a 100' cord? Each is 1800 watts and 110/120 volts. If each calculates out to 15/16 amps, does it need 30 amp rated cord? They are each induction single hot plate.

  8. I have a diesel truck with a block heater and the closest outlet is about 300 feet away. Can I use a 250 14 Guage extension cord with another 50 foot cord? Is this safe and will it have enough power to still make it work? Please let me know or if you have any other suggestions

  9. I have a commercial backpack vacuum. It states it is an 11.5 amp machine. It has an attached 50 ft power cord. Can I safely use a 50' or 100' - 12/3 extension cord, rated at 15 amps?

    Thank you.

  10. I have a 100' ext. cord that says "style 10". Is that referring to the wire gauge? It's rated for 600v.

  11. I mention above looking for allowable current drops in additional cord lengths. The link below should help anyone wanting the same information. While the calculator is designed for voltage drop, the resistance in the chart can be used for the current calculation. Simply use the same equation (V=IR) but keep the voltage constant and adjust the resistance based on length. Thus, I=V/R provides you the current drop over the specified length of cord.

  12. I would like to build a work light for my grinder. What is the best material and what type of wiring should I use? Any and all information will be greatly appreciated.

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