Magnet Wire

Data Tables for Solid Round Wire

Thank you for visiting the JavaScript Wire Table. Clicking the radio buttons below sends HTML to the second frame, listing wire gauge details for the chosen configuration.

Wire Table Options
Units: US Metric
Metal: Copper Aluminum

American Wire Gauge System

There are many sources of wire table information for round magnet wire (see references below). Most refer to the American Wire Gauge System, where gauge numbers increase in sequence as wire diameter decreases exponentially. Wire diameter can be calculated directly without using a lookup table with a simple exponential formula fit to the wire diameters at two gauges. 4/0 gauge which is 0.460" diameter and 36 gauge which is 0.005" diameter can be used to obtain excellent agreement with published tables. Note that 4/0 just means "four zeros" and sometimes appears as 0000. Numerically, 4/0 is represented as -3 when calculating wire diameter.

I've based my table data on the resistivity of IACS copper at 20°C, which is 1.7241 × 10-6 Ohm-cm. I've used 2.828 × 10-6 Ohm-cm for aluminum. To calculate weight for different wire gauges, I've used a density of 8.89 g/cm3 for copper and 2.701 g/cm3 for aluminum. These numbers can vary depending on the purity and treatment of the metal. They will also vary dramatically with temperature, especially resistivity. These numbers are only good at 20°C, which is typical room temperature. Obviously, in many applications the wire will be carrying current and can be much hotter than room temperature. I may add a feature in the future to allow you to enter a different temperature when obtaining wire table data. In case you are wondering why I included weight in this table, there are two reasons. First, spooled wire is often sold by weight instead of length. Second, the weight of a finished coil can be critical in many applications. Think "voice coil", as in loud speakers and microphones.

The diameters given here are for bare round wire, but most wire in real applications has a layer of insulation on it. For hookup wire and telephone cable you can easily strip off the insulation to get a good measurement of diameter. For magnet wire, getting a good reading is more of a challenge. You can scrape or sand off the insulation, but you will likely remove some copper as well. I've been burning the insulation off of magnet wire with hot solder, and then removing as much of the solder as I can before measuring diameter. Magnet wire insulation seems to run from 0.0005" to 0.001" thickness, so in many cases you can estimate a wire's gauge number with the insulation on. Obviously, these tables won't help if you have square or stranded wire. A good way to get started looking at different wire gauges is to buy the assortment carried by Radio Shack under their catalog number #278-1345 which contains spools of 22 ga., 26 ga., and 30 ga. enameled magnet wire. To measure diameter you'll need a good micrometer like the Mitutoyo in the picture above, or a dial caliper that reads in 0.001" increments.

JavaScript Implementation

This page contains a set of JavaScript functions which I've written to calculate wire table data based on your choices in the "Options" form. The data is then formatted in a table and written out as HTML text to your browser window. When the data is written out it completely replaces the contents of the target window or frame, so I have the table data sent to a second frame so this one doesn't disappear. That means that to view this page correctly your browser needs both frames and JavaScript. I've tested on quite a few combinations of platform and browser, and have obtained generally good results all the way from Netscape 4.x and MSIE 3.x through Netscape 7.x and MSIE 6.x on a variety of Windows and MacOS boxes. I've also done a little testing with Netscape and Mozilla under Linux.

All browsers I've tried can view the page correctly, and let you change the Wire Table Options. Some browsers have trouble when reloading, or using the "Back" button, and printing of frames doesn't always work. I find that selecting some text in the frame you want to print often helps. Send me some email (address below) if you find something that doesn't work right. Some browsers will let you view the source code for this page directly. But, in case yours doesn't, I've zipped up the whole directory for you to download here. As always, only you can determine if this code meets your requirements in your application. And, only you know if you are qualified to make modifications.


  1. Chuck Musciano & Bill Kennedy, HTML: The Definitive Guide, 3rd ed. Sebastopol: O'Reilly & Associates, Inc., 1998.
  2. Martin Webb, Michel Plungjan, & Keith Drakard, Instant JavaScript, New York: McGraw-Hill Companies, Inc., 2001.
  3. Robert C. Weast, ed. CRC Handbook of Chemistry and Physics , 64th ed. Boca Raton: CRC Press, Inc., 1984.
  4. Mark Williamsen, "Calculating Wire Design Factors", Machine Design October 12, 1989, p. 99.
  5. Magnet Wire General Engineering Data, Canada: Alcatel Magnet Wire Inc. 1996.

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