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Understanding Wire Gauges | Ask This Old House

In this video, This Old House master electrician Heath Eastman teaches host Kevin O’Connor about wire gauges and the applications for different size wires.

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Master electrician Heath Eastman gives host Kevin O’Connor a lesson on wire sizes. Heath displays different wire sizes, ranging from thin to thick. He explains how each wire type gets its name and gives Kevin some examples of what each wire might be used for.

Wire sizing can be confusing. AWG? Aught? 14/2 vs 14/3? What does it all mean? Master electrician Heath Eastman teaches host Kevin O’Connor what these sizes mean and what wires of different sizes are used for.

Where to find it?
Heath explains the range in electrical wire gauges and how they vary depending on the load needed for a specific appliance. Electric current has a limited capacity dependent on the size of the wire. Circuits are available in different voltage loads to provide the exact amount of electricity required for a particular appliance. The larger the wire, the more current it can carry, meaning large wires support heavier electrical loads and smaller wires support lower loads.

Electrical wire can be found at your local home improvement store.

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From the makers of This Old House, America’s first and most trusted home improvement show, Ask This Old House answers the steady stream of home improvement questions asked by viewers across the United States. Covering topics from landscaping to electrical to HVAC and plumbing to painting and more. Ask This Old House features the experts from This Old House, including general contractor Tom Silva, plumbing and heating expert Richard Trethewey, landscape contractor Jenn Nawada, master carpenter Norm Abram, and host Kevin O’Connor. ASK This Old House helps you protect and preserve your greatest investment—your home.

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Understanding Wire Gauges | Ask This Old House
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24 Replies to “Understanding Wire Gauges | Ask This Old House”

  2. Oh come on, nowhere does anything suggest that a blender can't be plugged into a bedroom. I don't know where this guy got that from, that's ridiculous. If the plug goes in the receptacle, it will work. Sheesh.

  3. i have a 2 feet extension running hot doing 15 amp and the air fryer i use is normally running max 10 amp what would explain that

  5. Back in the late 1970s we ran 4/0 in our church, the job supervised by two master electricians. I recall the wire was so huge and stiff I thought we would never get it through the big conduit but we finally did. It was a service to a large air handling unit as well as duct heaters and other electrics for a portion of the building. I'm grateful for the explanation.

  7. I would say more important than "right wire to the right appliance" is to say "right wire to the right breaker"… You get this combination wrong, that is when your house is at risk.

  8. It may cost more but I just use 10 gauge no matter what the circuit is for or how big the breaker is.

  9. Thank goodness for the simplicity of the metric system. Cable size is the cross sectional area in mm2.

    Generally in a domestic situation we use 1mm2, 1.5mm2, 2.5mm2, 4mm2, 6mm2, 10mm2, 16mm2.

    We use 2 core and earth (for single phase loads), and 4 core and earth (for three phase loads).

  10. Heath got it wrong. kcmil is not "circular millimeters" and it's not metric. It is thousands (k for kilo) of circular "mils" where a mil is 1/1000th of an inch. (A 500 kcmil conductor is 253 square millimeters in cross-sectional area.)

  11. While the ‘k’ does stand for “kilo” and the ‘c’ stands for “circular”, “kcmil” is not a metric unit of measurement, and the “mil” is not short for millimeter. One mil is 1/1000th of an inch, and a circular mil is the area contained in a circle with a diameter of one mil. A 500 kcmil conductor, therefore, is a conductor whose cross-section has an area of 500,000 circular mils.

  13. One thing you could have added was where "gauge" came from. it comes from the number of times the wire had to be drawn through a die or form to get it to the desired size. So, 14 gauge would would have been drawn through 14 sets of dies to get it to that size. Today it's a cross sectional area is more rigidly defined, but that's roughly equivalent to that. The X/0 sizes (pronounced "X ought") is just the number of 0s in that size, similar to "00 buckshot."

    Also should have mentioned that wire size is not only determined by the amount of current going through the wire, but also the length and duty cycle of the device you're powering. Consult you local electrical code or electrician for more information.

    And there was one mistake. MCM or kcmil is in imperial units. A mil in this context is 0.001 inches.
    https://en.wikipedia.org/wiki/Circular_mil

  14. very good video im a electrician good explanation on the awg of wire n uses

  15. My 70s tract home is all 8 gauge, the wire stripper tells me so. This is strange to me because it's hard to find 8 gauge in the stores nowadays at all.

  18. My house is wired with the yellow but only two wire …only ground is from box to water pipe and glass fuses and paper wound mains … id dare say my box is only 75amp .. even the drop from street is half the size of rest of neighborhood ,,, house was partially rewired in the 70s … all they did was run new wires to outlets

  19. Any downside for using 10 AWG or 12 AWG when only 14 AWG is needed – other than maybe the cost?

  21. Making money is an action, Keeping money is behavior, Growing money is knowledge..

  22. This is a little misleading. Yes the colors are standard now but back in the day they were not. My house was built in the 70s and both the 12 and 14 AWG wire have a white jacket.

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