Ohms Law Calculator

Ohms Law Calculator

Welcome to Vaping Hardware’s Ohms Law Calculator!

For those of you unfamiliar with Ohms Law, this calculator allows you to determine whether the coil, tank and mod you’re using will work safely together. This is especially important when using a mechanical mod or unregulated device.

Just fill in two of the below fields and the calculator will work out the rest for you!

If you’re unfamiliar with Ohms Law and how it relates to battery safety, please take a look at our guide to Ohms Law!

Please note, you only need to enter two of the below values. If you enter three the calculator won’t correctly work out the remaining value.

We’ve included a handy FAQ at the bottom of this page!

Enter two values into the form below:

Resistance  (R)   Ω
Current  (I)   Amp(s)
Power  (P)   Watt(s)
Voltage  (V)   Volt(s)


It’s always useful to at least have a basic understanding of Ohms Law as it relates to vaping. Especially when you’re using a mechanical/unregulated vaping device or building sub-ohm coils with a resistance of less than 1ohm. Ideally, you should be aware of the correlation between resistance, current, voltage and power to prevent drawing excessive current from your battery.

For obvious reasons, putting too much strain on the battery you’re using is not a good idea!

Using Ohms Law, Voltage (V) = Current (I) X Resistance (Ohms). Alternatively, Voltage can also be derived from Power (W) / Current (I) or the Square Root of Power (W) X Resistance (ohms)

Using Ohms Law, Current (I) = Voltage (V) / Resistance (Ohms). Alternatively, Current can also be derived from Power (W) / Voltage (V) or the Square Root of Power (W) / Resistance (ohms)

Using Ohms Law, Resistance (Ohms) = Voltage (V) / Current (I). Alternatively, Resistance can also be derived from Voltage (V) Squared / Power (W) or Power (W) / Current (I) Squared

Using Ohms Law, Power (W) = Voltage (V) X Current (I). Alternatively, Power can also be derived from Current (I) Squared X Resistance (Ohms) or Voltage (V) Squared / Resistance (Ohms)

Thanks for using our Ohms Law calculator, we hope you found it useful! If you’ve got any questions, feel free to drop us a comment below!

If you’d like to share this calculator with your friends, please hit the share buttons underneath.

Happy vaping!

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Comments 4

  1. How do I calculate Ohm’s Law when in TC mode? I’m running 0.64 ohms, but the wattage fluctuates: about 25 watts when I first fire up, then drops down to about 15. Input wattage in TC mode is 100, cut-off voltage is 12.

    1. Post

      Hi Ross,

      Ohm’s Law remains constant regardless of whether you’re using a Mod in TC mode. If you want to know a bit more about Ohm’s Law then have a look at our guide to understanding Ohm’s Law. The TC mode means your Mod is controlling the temperature of your coil with pre-determined settings.

      We usually talk about Ohm’s Law when it comes to a mechanical unregulated Mod. As your using TC mode you must have a regulated Mod, in which case Ohm’s Law is calculated slightly differently. You might find our Battery Amp Draw / Drain Calculator useful in telling you some more information about the setup you have. You mention though that your cut-off voltage is 12V which suggests you’re using a triple or quad battery Mod? Is this correct?

      Unfortunately I’m unsure why your wattage is fluctuating around 20W. Please can you expand on what the problem is or what it is you want to measure?

      Thanks for the comment Ross and hope the information above helps.

    2. Hey kinda first time trying to understand all of this brought a new tank to replace and old one how ever feels like my internal battery mod is struggling to heat the coil up so tried to understand ohms law to figure out best course of action , used calculator and came up with these figures
      My battery mod does not go any higher than 80watts so I can probly already guess what will be said ‘get a more powerful battery’ 🙂 any information on this type of issue would be much appriciated

      1. Post

        Hi Nathan,
        Thanks for your comment. When using a regulated mod, Ohms law is only applicable to the output side of your setup i.e. the tank. Wattage is fixed by the user and the battery current and voltage will be adjusted by the on-board chip to provide that wattage. Ohms law works perfectly for mech mods. Our https://vapinghardware.com/calculators/battery-amp-draw-calculator/ will give you a better understanding of whats happening on a regulated mod.
        Not sure what tank/coil you’re using but if may need more wattage to achieve a good vape. Most coils specify a min/max wattage they like to work at. 80W should be high enough for most stock coils.
        Hope this helps, if not get back in touch with the tank and coil you’re using so we can try and help you more.

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