Professional Tool Reviews for Pros
After searching the Internet recently, we realized people needed a definitive extension cord size chart. Understanding wire gauge proves difficult in some situations. This chart breaks down how both the wire gauge and length of an extension cord affect its ability to convey power to a corded tool. Running a 15-amp tool? How about a full 20-amp tool? We can help you understand what length and gauge extension cord gets you and keeps you up and running.
That’s right, we’re giving you the chart right up front without making you read through paragraphs of text. If you want to know more, like what is AWG or American Wire Gauge, see below. However, if you simply want to know what gauge extension cord you need to support a particular amount of amps, or how long an extension cord you can run without losing power, here you go. Getting a firm grasp on understanding wire gauge and amps and how they interrelate can protect your tools and keep you safe.
We broke our charts down by extension cord length since that’s where most people start when looking for the right gauge cord:
If you want to run a 100-foot long extension cord, you have to take into account the fact that you’re essentially creating a huge resistor. With that in mind, you typically don’t see 100-foot cords exceeding 15-amp (15A) capacity.
*Yields a 5% voltage drop—the maximum allowed in our calculations. Consider using the next size up for anything that is at or near 5% or—even better—opting for a shorter cord whenever possible.
See below for some recommendations on extension cords which should match the above requirements.
For our extension cord size chart calculations, we assumed 120V single phase with a power factor of 1. We also utilized the 2014 NEC Chapter 9, Table 9 numbers for impedance and voltage drop calculations.
We also allowed for up to a 5% voltage drop—which some people might consider too high. With that being the case, only one of our recommendations hit that level, the 100-foot 12-gauge extension cord with a full 15A draw. This might be an unusual application for some, but we felt it represented a great scenario. It helps you understand what happens when using a 100-foot extension cord on a tool with a high current draw.
Everyone on a job site or remodel has some experience with running extension cords. For larger tools that require them, it’s not enough to simply tap into the temp power pole or a nearby outlet. You have to ensure that if your tool requires 15 amps, it gets 15 amps. Use an extension cord that doesn’t carry the correct thickness (gauge) wire and you “starve” your tool.
But, you also do something worse. First, you can tax the tool motor—causing it to work harder to draw the energy it needs to run. Think of this like trying to breathe through a straw. If that straw isn’t large enough to deliver air, you struggle to breathe. That’s your tool on an improperly-sized extension cord.
Secondly, you potentially create a dangerous situation. An undersized extension cable will heat up over time. Use it in that state for too long, and the wire insulation could melt. This particularly holds true if you keep the wire in a coil, which creates resistance and a magnetic field that heats up.
Hopefully, you found our extension cord size chart helpful and direct to the point. Understanding wire gauge and amps and how to properly size your cords for the tool and distance can make your tools last longer and run more optimally. You may also want to see our article on what kind of extension cord do I need for even more info.
When he's not remodeling part of his house or playing with the latest power tool, Clint enjoys life as a husband, father, and avid reader. He has a degree in recording engineering and has been involved in multimedia and/or online publishing in one form or another since 1992.
Clint’s career has covered nearly the entire realm of audio and video production. After graduating at the top of his class with an Associates Degree in Recording Engineering, he began working for the famed Soundelux studios in 1994, one of the largest post-production companies specializing in audio for feature films & television. Working on a myriad of feature films, Clint honed his skills as a dialogue editor, foley editor, and sound designer. Years later, he moved into the expanding area of video editing, where he served as the company’s senior AVID video editor for three years.
Working for such clients as Universal Pictures, Hollywood Pictures, Paramount Home Entertainment, NASA, Universal Studios, Planet Hollywood, SEGA, NASCAR, and others, Clint dealt extensively with client management as well as film & video editing, color correction, and digital video & MPEG compression. He also carries several THX certifications (Technician I and II, THX Video), and is ISF Level II Certified.
After founding the CD Media, Inc. publishing company in 1996, he went on to help start or grow several successful online publications, including Audioholics (as Editor-in-Chief for 12 years), Audiogurus, and AV Gadgets. In 2008, Clint founded Pro Tool Reviews followed by the landscape and outdoor power equipment-focused OPE Reviews in 2017. He also heads up the Pro Tool Innovation Awards, an annual awards program honoring innovative tools and accessories across the trades.
Crediting his excellent staff for the success of what is now the largest power tool review publication in the industry, Clint DeBoer hopes to see continued growth for the company as it rapidly expands its reach. Pro Tool Reviews critically reviews hundreds of hand tools, power tools, and accessories each year to help inform users about the best and newest products in the industry. Reaching everyone from the construction industry professional and tradesman to the serious DIYer, Pro Tool Reviews helps tool consumers shop better, work smarter, and stay aware of what tools and products can help put them at the top of their game.
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what size extention cord do i need for a residental deep fryer
What gauge extension cord for 1.5hp pump motor 50 ft long for above ground pool do I need
I am an elderly female, and amps and volts are greek to me. I purchased a Teromas tire inflator and tried to operate it using a 50 foot extension cord. The tag on the cord says 125V and 10A. I have no idea if this is the reason why the inflator will not hold the pressure that I program into it. It always falls back to 1.10 or 0.00 before the power can be activated. Unless I can find an answer, I have wasted $70
My 2 cents worth. The voltage drop calculation should include the length of the wire run from the receptacle being used back to the electrical panel from which the receptacle is being fed. As an example, in wiring a house, it is not uncommon to run #14 wire to two or three outside receptacles. The wire length of that run could be from the panel to the first outside receptacle forty feet in length. The second receptacle could be on the opposite side of the house with a wire run 60 feet long. Add that 60 feet, to the 40… Read more »
Clint, good job for a “young buck” on a needed topic for DIYers & young trades workers. Suggest explaining why you should uncoil the longer cords. Also, as a cost motivator for the tool owners: I’ve seen 15 amp corded drills & saws burn out the triggers, & melt the varnish of the windings in the stator & commutator, making repair of the tool impossible. As the tool sees lower voltage, the amperage draw goes up to maintain the same/equivalent power. For single phase motors the formula is volts x amps = watts. Drawing more amps than the tool is… Read more »
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Professional Tool Reviews for Pros
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