What is Ohms Law?

Ohms Law is used to determine the current, voltage and resistance in any circuit. A personal vaporiser is a circuit in itself.

The formula for Ohms Law is:


In other words, when it comes to a device which has resistance to an electric current passing through it, its current in amps (A) is equal to its voltage in volts (V) divided by the resistance – R – in ohms (Ω).

I is the current in your device, which is measured in amperes.

The current is the amount of electricity flowing through the device.

V is the voltage, which is a measurement of the potential difference in energy between two points in the circuit.

As vapes can have a variable voltage setting, it’s important to know how changing the voltage will impact on the performance in this equation.

R is resistance, which is measured in ohms (Ω).

Sub-ohm vaping involves vaping with a total resistance of less than one ohm.

The amount of resistance in a circuit will have an impact on the amount of power a vaper gets out of their device.

Below is an infographic that includes voltage, resistance, wattage and amperage.  Amperage is probably the most important thing to consider when sub-ohm vaping.  The reason is simple – If the battery exceeds the amp limit, it may vent dangerous chemicals – or even worse – explode.

If you’re using RBA’s PLEASE ensure you’re vaping at a level your 18650 battery (batteries) can handle!

Please note this this chart does not take into account any other variables which may come into play.  Only you can determine if you are vaping safely.



Remember, this is simply Ohm’s Law transcribed on paper and does not take into account any other variables which may come into play.  Only you can determine if you are vaping safely.  My advice is that if the eJuice tastes good and the vapor production is satisfying, then that is the important thing.  Just make sure you are not overdrawing your battery.

Using battery ratings and coil resistance to vape safely

Now that you know about your battery ratings we need to know how to use the battery ratings with your atomizer coils resistance to ensure you’re vaping safely. If you do not know your resistance you can purchase an ohms reader almost anywhere vaping supplies are sold. Now that we have your resistance in ohms as well as all 3 ratings your voltage or “v” your storage capacity or “mAh” and your Amperage rating in either “A” or “C”. We will use these numbers to figure out your maximum continuous discharge of your battery and how much current your device will discharge. If your battery has an “A” amperage rating then you already know your maximum continuous discharge but if your battery uses a “C” amperage rating you will need to convert the “C” rating into an “A” rating. To do this is quite simple. Take your batteries “C” rating and multiply it by the storage capacity in mAh. For example if your battery is rated 10C, this means the battery is rated for 10 times the capacity of the battery measured in amps. So a battery rated at 1600mAh equals 1.6 Ah will therefore have a max continuous discharge rate of 10 X 1.6 = 16A. Now that we know the continuous maximum discharge rate of the battery we need to figure out how much current your device discharges and is it at a rate that is safe to vape. We can then take your batteries amp rating. You can then take your batteries voltage (4.2v fully charged) and divide it by your atomizer or coils resistance to get your actual discharge rate. Now compare the two. The current your device draws must be lower than your batteries amperage rating. For example 4.2v / 1ohms = 4.2A discharge rate while 4.2v / .5ohms = 8.4A. Remember your devices discharge rate must always be less than your batteries amp limit.