I am looking to build a small Tesla Coil at home with limited supplies. I am reasonably confident (well.. as confident as a biologist can be!) with my calculations so far, however I have hit a mental wall while trying to work out what gauge wire I should use for my secondary coil.

I would like to know how to calculate the gauge of wire I need to buy. The information I have is the height of the tube I will wrap it around, the diameter of the tube and the number of turns I want.

For my coil specifically the rough plan is to have wire coiled 13.5cm high around a 3cm diameter tube (the tube itself is taller and I have allowed for space to attach it to the other parts) and I am aiming for around 1200 turns, however if when I find out how to do this calculation the wire is too thin I will use fewer turns.

Any help would be greatly appreciated, I can tell this is a simple question, I have over complicated it in my head!

  • \$\begingroup\$ How did you get to 1200 turns and what output current are you anticipating? \$\endgroup\$
    – Andy aka
    Commented Mar 16, 2015 at 10:56

1 Answer 1


It should be fairly obvious that you need to lay 1200 wires side-by-side in a space of 13.5 cm, so each wire (including its insulation) needs to be no wider than

$$\frac{13.5 \text{ cm}}{1200} = 0.1125 \text{ mm}$$

This would correspond to roughly AWG 38 with about 6 microns of enamel coating. I have no idea what the actual thickness of magnet wire coatings are, so you may need to adjust your figures to suit. Some online sources suggest that it's on the order of 0.0002 in., which would be about 5 microns.

  • \$\begingroup\$ I recall reading that you want the secondary length to be a quarter wavelength of the resonant frequency of your primary - is that right? So then does it really matter what gauge is used? \$\endgroup\$
    – docscience
    Commented Mar 16, 2015 at 4:28
  • \$\begingroup\$ @docscience: No, that isn't right. \$\endgroup\$
    – Dave Tweed
    Commented Mar 16, 2015 at 4:56

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