Carbon fiber heating coil power calculator

A bunch of projects I try to do end up essentially being “put a heater somewhere”. Most of the time I don’t really know what I’m going to do or what size heater I’ll ultimately want. At the the same time, I want the lowest power heater possible to decrease the chance I’ll burn anything down.

I’ve purchased a variety of small heaters, and they all work. They also cost 10-20$ and only come in the sizes they’re sold in. This makes everything a pain in the butt AND I have to wait for them to show up. As with everything, the less you want to pay the lower the chance you’ll get what you want when you want it.

After looking at a bunch of different options, I’ve recently purchased multiple rolls of different carbon fiber heating cable. When ordered from China, it’s ~25$ USD for 100m. I got 4 different rolls, identified by the number of strands of carbon fiber – 1k, 3k, 6k, and 12k. These, respectively, have resistances of 400 Ω/m, 130 Ω/m, 61 Ω/m, 33 Ω/m. That means I can now create a heater of all sorts of different shapes and powers!

The one big thing to be aware of is the heating cable can only get so hot before it burns down the house. One of the listings I purchased from mentioned 25 watts per meter as the max power. Now to do math to figure out which specific coil at which length for a given geometry.

After trying (and failing) to keep the numbers straight I decided to make a quick calculator:

Put in the resistance per meter and the length, get out the total power and the power per meter. Very niche but very helpful! As an example, one of the heaters pictured above is ~18 W. To make it out of the 3k cable I need 2 meters, meaning I am paying an equivalent of ~0.60$ CAD (+ a few cents for 3D printed holder). Hard to beat that price!

Site is available here:

3 thoughts on “Carbon fiber heating coil power calculator

  1. Sanford

    I like your calculator. Thanks. Would be helpful if it would accept fractional meters such as 0.5, 2.75, etc. I am working with low wattages for small foam incubators.

    1. tobymurray Post author

      Glad you found it useful, and good point – I’ll fix that soon, there’s no reason for it to stick to integers.

    2. tobymurray Post author

      I’ve updated the calculator to take hundredths of a ohm/meter and length – thanks for the suggestion!

      I also added a title so it’s a little more informative.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s