# Extension Cords Size Chart

*"Electricity encounters friction as it travels through electrical wires. Knowing this, use only as much extension cord as you really need. I can call you on the phone to answer your extension cord questions so you don't get KILLED or BURN DOWN YOUR HOME. The call is FREE if you're not satisfied with my answers. CLICK HERE to set up the call."*

## Extension Cord Sizing Checklist

- Determine amperage of tool/appliance
- Calculate cord length - use the shortest possible cord.
- Wire gauge determines amperage load
- Watts = Amps X Volts Example: 2,400 watts = 20 amps X 120 volts
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The size of your extension cord is very important. If you undersize one you can start a fire or ruin an expensive tool.

Fortunately, many common small hand-held 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.

## How Do You Start to Size an Extension Cord?

You start to size an extension cord by obtaining the motor amperage from the plate on the tool. You'll 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.

What is Ohms Law?

Ohm's law is a physics principle that helps keep you safe with electricity. In it's simplest form, volts multiplied by amps equals watts.

Think about a light bulb. They're often sized by watts. The voltage in most circuits in USA homes is 120 volts. You may have a circuit breaker panel in your garage that has 15 or 20-amp breakers. All of these things concern Ohm's 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 equal 5 amps (120 x 5 = 600).

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## What is Voltage Drop?

Voltage drop is the loss of voltage as it travels down a long wire.

Voltage drop is real. 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.

### Can I Have Multiple Tools On 1 Cord?

Yes, you can have multiple tools operating on one extension cord. You just have to be sure the cord is large enough to handle the loads.

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.

## How Do You Size an Extension Cord?

You size an extension cord by first determining the appliance or tool that will be plugged into the cord.

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

## Is the Length of the Cord Important?

Yes, the longer the cord is the greater the voltage drop will be. If you must go a distance greater than 100 feet, then upsize the extension cord.

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.

## What Does Wire Gauge Mean?

Wire gauge is the measure of the diameter of the metal conductors in the extension cord. Common extension cord wire gauges are:

- 18
- 16
- 14
- 12
- 10

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!

## What Load Can Each Gauge Wire Handle?

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.

### Why Does my Circuit Breaker Trip With the Right Cord?

Your circuit breaker may trip because the tool you're trying to power draws too much current. This is very common if you're trying to operate a large table saw cutting thick wood.

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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### Do Other Things on a Circuit Add to the Load?

Yes, 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.

B174

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.

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.

250 feet of 10 ga extension cord. How much voltage and amps should I expect at end.

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.

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.

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.

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.

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

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.

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

I need to run power off a 250 ft extension cord

What size wire do I need to get the most out of the curd?!

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.

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

I am looking for the proper extention cord for a 5" ac/dc grinder.

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.

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.

My mom wants to use a 16 AWG extention cord to plug in her heated water bowl for her birds outside. The bowl says it uses 60 watts. Is that ok?

That's fine. Since the cord is outside and in COLD WX, it helps prevent any overheating. It's not going to overheat with just a 60-watt load.

Make sure there is a ground fault interrupter so the birds don't get electrocuted taking a bath

Hello experts ,

I know you guys probably covered everything but I have no idea whats going on So i will ask here I have a Heater which is rated 2000 W 250 V . I have an extension cable 10 ft which is rated 6 AMP and 250 V is it safe to run the heater on it ? If not which cable should i get thankyou veryyyy much in advance please answer ♡♡

No it's not safe. The formula is:

Watts = Amps X Volts

Your heater draws 8 amps. The cord is rated for 6.

Hi Tim,

Thanks for this write up. I am planning to build a shed, the nearest outlet is 200 ft. I’ll be running a 12” chop saw that runs at 15amps. Will a 12/3 do the trick and can I run 2 100ft cords, or is a 200 ft necessary?

Thanks

Shane

Shane, you should run a proper electrical circuit with buried cable to a box in the shed, not string extension cords since this is obviously a repetitive use scenario and seemingly going to be your workshop where it will be handy to have power for many things, including lights.

Run 10/3 to two, 15A outlets.

I have leaf blower with a 12 amp motor. Right now, I am using a 50' 16 gauge extension cord but want to move up to a 100' cord. I am looking for a 14 gauge cord now but I have seen some conflicting information. One package I saw said 13 amp and 1625 watts, which sounds right based on 125 volts. I saw another 14 gauge cord that claimed 15 amp, 1875 watts. Still another says 13 amp, 1875 watt. The last claim doesn't seem right. My question is, can you have a 100' 14 gauge cord that will handle 15 amps and 1875 watts? And, is it possible to have a cord that claims to handle 13 amps AND 1875 watts?

Watts = Volts X Amps

A 14-gauge wire can only handle 1800 watts. PERIOD.

That's assuming the AC is 120 volts.

No, Kenny. The current flow is the same. The VOLTAGE drop is higher, which leads to lower watts at the end.

Most equipment is rated for a certain tolerance of % voltage drop. I've seen 3-5% used, which actually matters at higher amps and distances. Depending on what tolerance you assume, you can have a need for a whole different AWG.

I need to buy a 50am 50 ft extension cord for my RV. What guard wire 10awg? to 6/3 /8/1?

I have a shop vac that requires 7.3 Amp. What would happen (if anything) if I use a 25 ft extension cord of 14 AWG? I realize that this cord delivers around 14 or 15 Amp. What would happen if the cord provides more Amp than the tool requires? Will I damage my tool? Thank you.

Tanner,

Great question! The short answer is using a larger sized cord will NOT damage your tool.

The best analogy might be: Imagine you're driving on the 205 Freeway in southern California, but you're the ONLY CAR on the giant road.

There's more than enough room on the road for you and there's no danger because there are no cars near you that can rub up against your car.

Does the maximum cord length for a tool based on it's amperage requirements include the cord length already wired into the tool?

You'd have to ask the electrical engineer that designed the tool. Yes, that's pretty much impossible. My gut tells me the answer to your question is "No".

Tim, a couple of other things about extension cords:

1. There are still retailers who sell non-UL cords, some of which have undersized grounding (green) wires. Always verify any cord you want to buy has a UL sticker.

2. If you see - or have - a cord that won't lie straight (has curves every foot or so) it's been damaged by too much current - got too hot. Discard it.

3. For safety, every cord used outdoors should be plugged into a GFCI receptacle, many of which are only rated at 15A. 20A GFCI receptacles are available, but cost quite a bit more so many builders won't use them unless the local code requires it.

Larry this is not necessarily true on #2. If it has curves that can merely mean the temperature is not high enough for the outer jacket to be very flexible, or even the copper (or gasp, CCA) inside, or it has gotten stiff from some time and UV exposure.

I have several cords that have definitely never been used with equipment that can exceed their ratings and do have some that have curves, especially when they are looped to less than about 2' diameter for storage. They have been like that for over a decade and still work fine.

Tim, great article. I had no idea there were so many considerations in using a (heavy duty) extension cord, as in using outdoors for my hedge trimmer. My question is while trimming a few weeks ago, I cut into the cord. Hubby taped it together with electrical tape but I haven’t used it since. Is it safe to use or should I get a new cord? It was a 100 foot, heavy yellow one.

Susan,

I can't really offer you the answer you want because I don't know how your main squeeze made the repair. Did he solder the wires? Did he use heat-shrink tape on each conductor? Heat shrink over the entire repair is much more desirable than electrical tape.

I don't remember the full details, but I think wire gauge is determined by the number of wires that will fit in a one-inch circle--only ten 10-gauge wires will fit in a one-inch hole; fourteen 14-gauge wires will fit in the same one-inch hole; sixteen 16-gauge wires will fit in the hole. This explanation will make sense of the smaller number being the larger wire. Please check the details before passing the information along.

Eleanor,

That's not correct. You can discover how wire gauge is determined here:

https://en.wikipedia.org/wiki/Wire_gauge

Hi Tim,

As always, thanks for good, useful information. This article is particularly helpful for keeping people (and their tools) safe! I once loaned my almost-new large Milwaukee angle grinder to a co-worker who was welding up some fence post assemblies to house his 9 Husky sled dogs. He burned out the motor using a too-small long extension cable. Note: he paid to have the motor rebuilt, so it ended well.

One small nitpick - I'm an electrical engineer so I find I must point out that Ohm's Law isn't really about watts (power). It's about the relationship between voltage ("V" in volts), current ("I" in amperes), and resistance ("R" in ohms, appropriately named). The formula is V=IR. Yes, it's very related to how much current a cable or cord can safely carry, and your piece does address that well, as determining the resistance of a cable isn't something easily done with readily available testers. Thanks for listening....All the best, and I loved the piece on rallying - congrat's on your Comm position!

I would talk to an electrician before doing it, an electric dryer receptacle is 240 volt 30 amps. Code permits a so-called 3 wire circuit of to 120 volt 30 amp circuits sharing the same neutral white wire. This is not a problem because all the neutral carries is the difference between the 220 volt circuits, it has to do with how the 120 / 240 volt Supply works and the center tap utility Transformer. Home Depot and Lowe's both sell 10 gauge 4 conductor rubber cord by the Foot. Also the connectors for both ends. In most jurisdictions it is legal to plug into the dryer receptacle and take off 2 120 volt 30 amp circuits with the 4 conductor 10 gauge wire. You absolutely have to wire this right so that's why you need an electrician do it, but you're using the red for one hot and the black for the other, and your green is ground and white the shared neutral. You also want to use two gfi's rated for 20 amps they are the ones that have the sideways slash in the receptacle. And definitely have electrician Wireless for you, and verify that it's legal in your location.

But this is how you can temporarily use a 20 amp device in a house that has electric dryer but only 15 amp circuits

We have a 12amp electric lawn mower and we need 100’ of extension cord...we purchased a 16 gauge is this going to be an issue??

Yes. It's TOO SMALL.

I'd be using a 12-gauge wire. Look at the table above.

Great info! But some web pages I've visited give me slightly differing opinions.

If I understand, you seem to say that I can plug my 6.5 amp refrigerator/freezer into a generator (in case of a power outage) using a 100 foot long 16 gauge extension cord.

The last page I visited:

http://www.diybyexample.info/2010/07/what-size-extension-cord-do-i-need/

says I'll need a 14 gauge 100' ext. cord.

I'll need all 100' of that cord since the generator is at my neighbor's house... but you're saying the 16 gauge should be ok?

Many thanks for your help with this.

Btw, Tim... my refrigerator/freezer is 6.5 amps but it also says 115 volts. Not sure if that would make a difference.

Great article, thank you!! There is much confusion about extension cords. Recently my brother and I found mom had cheap extensions, some daisy chained throughout her house in practically every room. A big terrible devastating just waiting to happen. We fixed and made sure they were removed and replaced with appropriately sized extensions.

Hi Tim-thanks for all your wisdom and assistance!

So: I have a detached garage that currently has no power in it. I would like to run some power tools in it, so I figured, in the short term, I'd use an extension cord. My highest amp draw would be a Century FC90 Flux Core welder. It's Rating Plate says it's I1max=20A, and it's I1eff=11.

The other tools I am liable to use would be Angle Grinders, a SkilSaw, Router and Jigsaw, but I would not be using those at the same time that I was welding. The only other thing that would be running while I was welding would be a 500 Watt work light, drawing 5 amps. I normally plug the welder into the laundry room outlet, which is a dedicated 20a circuit, in a house built in the 50s. The laundry circuit was equipment grounded by us when we moved in.

So the plan is, if I could, to plug the extension cord to the laundry room outlet, and run it out to the garage. The question is: what gauge would work? I could take one of two routes: one is, at last measurement, 62 feet, but would come with greater hassle (putting a hole in a door, or the wall), and the other is pretty much a full 100 feet (more convenient, but longer, and generating yet more resistance).

I was looking at a 10 gauge extension cord. Would I need that gauge, or could I get away with 12 gauge?

Hi Tim-thanks for all your wisdom and assistance!

So: I have a detached garage that currently has no power in it. I would like to run some power tools in it, so I figured, in the short term, I'd use an extension cord. My highest amp draw would be a Century FC90 Flux Core welder. It's Rating Plate says it's I1max=20A, and it's I1eff=11.

The other tools I am liable to use would be Angle Grinders, a SkilSaw, Router and Jigsaw, but I would not be using those at the same time that I was welding. The only other thing that would be running while I was welding would be a 500 Watt work light, drawing 5 amps. I normally plug the welder into the laundry room outlet, which is a dedicated 20a circuit, in a house built in the 50s. The laundry circuit was equipment grounded by us when we moved in.

So the plan is, if I could, to plug the extension cord to the laundry room outlet, and run it out to the garage. The question is: what gauge would work? I could take one of two routes: one is, at last measurement, 62 feet, but would come with greater hassle (putting a hole in a door, or the wall), and the other is pretty much a full 100 feet (more convenient, but longer, and generating yet more resistance).

I was looking at a 10 gauge extension cord. Would I need that gauge, or could I get away with 12 gauge?

No No No and Hell No.

Do this job the correct way and install a subpanel in the garage that's rated for at least 40 amps MORE than the draw of the welder.

Run the 240-volt power line from the house to the garage in approved conduit buried at least 2 feet into the ground or whatever the current NEC requirement is.

Trying to do this with an extension cord is both foolish and DANGEROUS.

Hi,

I have a Champion generator with 7500 running watts and a 30 amp breaker internal to the generator. What's the longest 10 gauge cord can I use to connect it to my house? Thanks!

A 100-foot cord will be fine.