Vape mods.

The Vaper’s Guide to Voltage, Watts & Ohms

Update: Feb 2021

Not so long ago a reader told me she was still completely confused about voltage, watts and ohms, and I have a feeling she’s not the only one. In fact, while we were writing this post, we had at least five emails from readers asking for an explanation!

So we’ve put together this tutorial for our Vape Academy. Before we get started, it’s worth noting if you are starting off with variable voltage/wattage, and even with different resistance coils, you can get a very good vaping experience without a deep understanding of the science behind it.

At its simplest level, it’s simply a matter of adjusting the voltage or wattage of the battery until you get the vapour, flavour and throat hit you desire. You can also experiment with using different resistance coils and combining them with different voltages/wattages.

After all, with most entry-level vape kits, all you need to do is: 

  • Check what wattage you can use with the coil in your device
  • Adjust your wattage and airflow until you get the vapour, flavour and throat hit you need. 

Some people want to know more to get the perfect vaping experience. If you’re one of them, this post is for you.


An introduction to voltage, watts and ohms

Advanced Explanation

What Are Ohms? A Simple Explanation for Vapers

Monks squat in front of a giant coil, chanting ohmmmmm.

An ohm (Ω) is a unit of resistance. Essentially, the lower the resistance of your coil, the more electricity will flow through it. Increase the amount of resistance and less electricity will flow through. So when you use a lower resistance atomiser, and more electricity flows through, you will find the following:

  • more heat is generated at the coil
  • more vapour is generated
  • you may experience a more intense flavour (however, flavours perform differently with different resistance coils)
  • vapour will be warmer

Depending on your tastes, the above may all be positives! On the negative side:

  • your battery will be drained more quickly
  • battery life may be reduced
  • vape juice will be used more quickly
  • coil life will be reduced (very low ohm atomisers may only last 2-3 days)
  • you are more likely to experience a dry hit. 

Since we first wrote this, new technology such as mesh coils, plexus coils, smart mode and auto-prime mode have been introduced. This helps reduce (but not eliminate) burnt coils

Obviously, when you use a high resistance coil the opposite will happen:

  • less electricity flow
  • reduced coil heat
  • reduced amount of vapour
  • cooler vapour
  • and you may experience a less intense flavour.

But on the plus side:

  • battery life will be longer
  • less e-liquid will be used
  • you will be less likely to get a dry hit.

What Ohm Resistance Should I Use In My tank?

Sub Ohm Vaping Chart

When we first wrote this post, we used to refer people to the chart above. 

While we’ve left the chart there, our answer has evolved!

That’s because:

  • new technology has entered the market
  • more vapers Mouth-to-Lung with low resistance devices
  • subtle differences in materials used can affect the wattage needed
  • manufacturers provide better coil guidance.

So unless you are making your own coils, check the manufacturer’s guidance. You can find this on product manuals and our website product pages. 

Variable Voltage and Wattage Vapes Explained

Sitting on a sofa vaping a Vision Spinner.
Dan from ecigarettedirect with a variable voltage Vision Spinner 2.

The resistance of your coil is not the only thing that affects vapour, flavour and throat hit. It also depends on the amount of power flowing through your coil.

There are two common types of vape batteries which allow different amounts of power to flow through your coil. These are variable voltage and variable wattage.

As we’ve seen, you can get a more intense experience by lowering the resistance of your coil.

You can also do the same by increasing the amount of power flowing through your vape device. That may sound complicated, but usually there’s nothing more to it than pressing an up/down button.

But what if you want more vapour again?

Then you can combine a low resistance coil with a higher wattage to get even more vapour. But this does come with its own problems. You are far more likely to burn coils or get a dry hit, and coil life is reduced.

Variable Voltage vs Variable Wattage Vapes

Morpheus meme: Reads -

The difference between variable voltage and variable wattage is a bit like the difference between an automatic and a manual car.

With a variable voltage device, you manually control the amount of power (voltage) going through your device.

The amount of energy that is actually output will depend on how the resistance of your atomiser interacts with that power flowing through it.

A variable wattage device is different. Rather than telling the device how much power you want to flow through your atomiser, you tell it how much power (wattage) you want it to output.

The variable wattage device will then automatically adjust the power going through the atomiser (the voltage) to produce the power output you need (the wattage).

To put it another way, watts is essentially how much power your vape produces and voltage is how much power is put through the device.

So, as you increase the wattage the voltage also increases and vice versa.

Voltage is not the only factor that affects wattage – you also need to take into account the resistance of the coils.

Lower resistance coils produce more flavour, vapour and heat at a lower voltage than higher ohm coils because they use more watts.

For example, if you have a 1.8ohm coil running on 3.7 volts you’ll get an output of around 7.3 watts.

If you change the coil to a higher resistance of 2.8ohms you will notice a considerable decrease in flavour, vapour production and heat. That’s because the wattage is lower (around 4.4 watts). You will need to increase the voltage to increase the wattage and get a better vape.

Because lower resistance coils use more wattage, they tend to generate more heat. This means they often burn out quicker than a higher resistance coil would.

Variable voltage devices are quite rare now, although many devices will display both voltage and wattage. The Innokin Coolfire Z80 is an example of a variable wattage device, and delivers 6-50 watts controlled by up and down buttons.

What Does mAh in Vape Batteries Mean?

mAh for e-cigs explained You’ve probably seen mAh used to describe vape. mAh is important because it measures how long a battery lasts.

Going back to our car analogy, if voltage is the fuel then mAh is the size of the fuel tank – the bigger the tank the longer the car will go before it needs refuelling. mAh stands for Milliamps per hour, but we’ll go more into that below.

What Is Sub Ohm Vaping?

Gif cloud chasing
James and Will from ECigaretteDirect Blowing Clouds with the Aspire CF Sub Ohm Battery & Atlantis Tank

We’ve seen that by lowering resistance and increasing voltage we get more vapour, more throat hit and sometimes more flavour.

Sub-ohming takes this further by vaping at a resistance of less than 1 ohm. 

At one point this was considered pushing the boundaries of vaping. But things have changed. 

The term sub-ohm, while still used, is not as relevant as it used to be. Coils below 1 ohm are common, and coils with a resistance of 0.8 ohms are often used for Mouth-to-Lung vaping. Even lower resistance coils, such as 0.15 coils, are often used for cloud vaping. 

Originally, sub-ohm vaping was reserved for experienced vapers who want to push the boundaries with rebuildable coils. The introduction of mass-market vape vape mods has changed all that.

For example, the VooPoo Drag 3 can fire up to a 177 watts and uses low resistance TPP coils for larger clouds of vapour. 

Vapers who want the largest clouds possible may still use a mechanical mod. These have no electrical safety switch and may increase the risk of a malfunctioning battery if not used correctly. 

Want to know how to sub-ohm sub ohm? See the Vaper’s Guide to Sub Ohm Vaping.

Advanced Explanation of Voltage, Watts and Ohms for Vapers

Ohms Law Vaping With EcigsVape devices use simple circuits that contain a battery, a switch and a heating coil. The circuit is effectively a controlled short, with the power output from the battery used to create heat.


A milliampere hour (mAh) is 1000th of an ampere hour (Ah). Both are used as a measure of battery capacity, a higher mAh rating means more capacity. mAh only measures capacity and should not be confused with power.


The Amp (short for ampere) is a measure of current. An ampere is defined as 6.241*10 18 electrons (1 Coulomb) per second passing through a point in a circuit.


Voltage is the amount of potential energy between two points in a circuit. One point will have more charge than the other. This difference in electrical charge between the two points is called voltage.


Watt is a measure of the amount of power consumed by an electrical device.

Ohms Law for Vapers

Cartoon demonstrating how volts, watts and ohms work. Image above from

Ohms law refers to the calculations used to show the relationship between voltage, current and resistance. There are three of them, which we’ve listed below.

  • V = Voltage measures in volts
  • I = Current measures in amperes (Amps)
  • R = Resistance measured in ohms

By knowing any two of the three values, you can calculate the third using ohms law;

  • V = I x R (Voltage = Current Multiplied by Resistance)
  • R = V/I (Resistance = Voltage divided by Current)
  • I – V/R (Current =Voltage Divided by Resistance)

So, if you are using a 0.5ohm coil on a battery that gives 4.2 volts, you use the following sum to work out how many amps the circuit is draining from the battery.

I = 4.2/0.5 = 8.4A

This is useful for vapers to know, particularly if they are making their own coils. The sum above is the most useful, as you should not be vaping on a coil when you do not know its resistance, or on a battery with unknown voltage output.

For those who prefer video, here’s a stellar explanation from New Amsterdam Vape.

You’ll find an excellent calculator which you can use to calculate ohms law here. Update: Shawn Hoefer has suggested also using the Ohmaster and CigToy apps. Given the importance of battery safety, he recommends using both rather than one or the other.

Sub Ohm Hardware

We’ve already mentioned the iStick Power and the VooPoo Drag 3 kit, both of which can be used for sub-ohm vaping. But if you’re looking for an all in one kit, you might want to consider the Innokin MVP5.

One of my favourite vape devices, the Innokin MPV5 can output up to 120 watts. Sure, there are devices with more power, but the reality is that unless you are building your own coils, you don’t need more than 120 watts of power. 

For a fixed battery device, this MPV5 has an unmatched capacity. At 5200mAh, this device can last for days without needing to be recharged/ on one charge. It also provides a great vape, and contains a whole host of unusual features such as flashlight functionality and the ability to act as a power bank.

Although not the newest available, one of our favourite tanks for clouds remains the Falcon II. The device comes with 0.14Ω coils and a conical mesh design which funnels air-flow up through the coil for serious clouds. 

In summary

There’s a lot to take in here, but this information is really for the enthusiast. Unless you’re into coil building, you don’t need a deep knowledge of the science to vape. 

The most important thing is to learn just enough about vaping to ensure you enjoy it – and don’t go back to smoking. 

55 thoughts on “The Vaper’s Guide to Voltage, Watts & Ohms”

  1. I have a friend, a retired Physics teacher, who explained all this to me some time ago (when I was considering sub-ohming). I shall now send him a copy of this Guide, to show him how he should of done it! 😉

      1. Hi my zenith tank 1/6 coil keeps showing up on my tank as 1.72 am running it at 12watts is tht okay 👌🏼

  2. Very informative article… I have always been a little worried about sub-ohm vaping, but the device you are offering in this Giveaway seems to be the perfect answer for people like me!!

    Thanks for the opportunity… <3

    1. Could not edit my post… but I hope this shows up!! 🙂


      1. I understand this article is old, but an update for the modern day of “everything is sub ohm, and rda’s are awsome!” Along with the newest accents in batteries and devices would be down right awsome!

          1. Hi James,

            I came across your artice (2015) so I hope you can help me, I have recently been given one of thosde chunky bos type ecigs. My problem is that I get a reading of W and for example 1.46 O but a zero reading for V. No matter how much I adjust the readings the V remains a 0. Is this normal or do i have a faulty device, hope your still around to put my mind at ease one way or the other, thank you.

  3. You missed one of the key benefits of ‘variable’ wattage devices – which is power management. As a vaper uses his/her device, the electricity stored in the battery drops. This will manifest itself as a drop in the voltage at output. Typically a fresh, fully charged battery will show 4.2 volts. As it is used this will drop to below 3.5 volts. Variable wattage devices compensate for this because what they deliver is a consistent wattage (V x I = W). Thus the user dials in the wattage required and the device delivers this until it alerts the user (most do) that battery power is depleted to the point and a charge/battery change is required.

      1. Hi I have coolfire z50 i am 1st user, I have a coil 0.8 coil in and I am vapeing at 6.00 watts is the set wrong? People have to me 10 to 18 whats or it would use my coil quickly? Confused!! I am using 50/50!

    1. @Bryan

      I know this thread is ridiculously old, but I felt the need to comment for anyone else that might stumble across it.

      Sorry, I have to disagree. Regulated mods are “supposed” to keep the voltage constant as the battery voltage drops as opposed to mech mods that give you whatever voltage the battery currently has. I don’t know if James covered this or not, because I just did a quick scan, but the benefit of variable wattage over variable voltage is that with variable voltage, the voltage is held constant. The coil resistance will fluctuate over time so the wattage (actual work done) will change based on the following equations:

      I=E/R and P=IxE Where E=Voltage I=Current R=Resistance.

      So, as “R” increases, then “I” decreases and “P” decreases given a constant voltage “E”. The reverse occurs as “R” decreases, obviously.

      Therefore, rather than adjusting the voltage to compensate for changes in the coil resistance over time to keep a constant wattage, which is what you want, you use variable wattage. The voltage is automatically increased or decreased to compensate for the change in the coil resistance. It’s less hassle. Not that big of a deal either way.

  4. Great tutorial/guide, I’m currently using aspire esp30w with a tobeco super tank 0.3 coil. At 10 watts using 2.0 volts, I get s refreshing hit from my oils. Will this burn my coil out quicker

  5. LOVE the wattage/voltage/resistance chart! I’ve never seen such a clear and useful resource for calculating ideal settings on my ecig…


  6. Hi
    When should you top up fluid in i sub tanks and can it burn out your coil or damage your device if you leave till very little fluid is left.

  7. sorry but im still pretty confused. I have a joytech vape with coils that i made myself and this is the first time im using my own built coils. before i changed my coils, my ohms were around 0.35ish and now that i made my own my ohms are at 1.04 and my box’s watts can be changed going all the way up to 80 watts. so im wondering if having my ohms that high is bad? and if so what can i do to fix it? i used kanthal wire i think 24 gauge but im not positive on the size wire. since im now using my own coils my vape has been running differently and not popping as much, which is what im used to happening. i just wanna make sure im not gonna catch this thing on fire lol someone help please! thank you~

    1. Hi Anna, this isn’t meant to be a guide for coil building, I am afraid. You would need to find a specialist guide, and our advice is always don’t do it unless you know what you are doing!

  8. Hi, I’m running a Cool Fire 1V with a 0.4ohm DCC coil in the Aspire Cleito tank and would like to know the amount of Watts you recommend. I currently am using it at 30W and am pleased with the results but Aspire rate the 0.4ohm DDC coils to be run at a min of 40W and max 60W. Should i be not be using this tank set-up with the CF1V?

    1. We used to make attempts to estimate the wattage to be used with different resistances but we tend to avoid that now because there are so many variables, and as manufacturers should know their products best we generally recommend following the manual. That said, I can’t really see the harm – it’s not as if you are using too high a wattage and are likely to burn out the coil, so if it works for you why not go with it?

  9. Thanks James, at least i now know that im not in any danger of burning my coil out quicker than it would normally but was wondering if running at 40W constantly (as this is the max watts the CF1V puts out) would be ok for the battery?

  10. Hi there,I recently bought the Istick power Nano from a vape store.I don’t know much about vaping as this is my first vapebox but when I bought it the guy behind me told me that although my box can vape at 40watts he told me not to go over 25watts as this would burn the coil out.Can you please tell me what coil I need to buy so I can vape over 25 watts.I would like to vape at 40 watts but just don’t know what coil to buy.The tank is a MELO 3 Nano.Thank you.

  11. Thanks, very informative piece.

    -minor editing needed as ‘the difference’ is repeated twice (just under the Matrix picture).

  12. Pingback: How to Choose The Best Vape Mod For You | Ashtray Blog

  13. I’m using 2 0.5 ohm coils but showing up as 0.33 on my mod and voltage at 5.54. I’m going at about 90w is this safe

  14. In wattages mode, i’m using 0.9 ohm single coil and set wattages to 45 watts. The voltages is shown on the screen more than 7 volts. However, my battery is only 3.7 volts (1 cell). The actual output should less than 45 watt right? Should I change the coil to lower ohm?

    1. Hi TTTOE

      Some devices will cap the wattage or voltage output according to the max available, seems yours doesn’t do this, and it’s trying to maximise the wattage despite the lack of voltage actually there.

      I’d suggest running a 0.9 Ohm coil at between 16-19W (3.8-41V).

  15. Absolutely informative folks I loved the knowledge I got from reading this and everyone’s comments. HOWEVER can someone please please please explain why when you buy a 0.05 ohm coil it’s not labeled as a sub ohm coil. Ok honestly I’ve been vaping a little over a year now but starting out I was looking for the chart to find the best temperature to vape at to achieve both flavor and throat hit once finding this never will you see a 0.05 ohm coil listing on there. I have the elef I stick pico with the Atlantis evo tank and over a year I’ve dropped this puppy multiple times and have only broke my glass 2 times

    1. Hey Mark, increasingly people are moving away from using charts and relying on manufacturers’ recommendations to achieve optimum power levels. That’s partly because manufacturers use subtly different materials in the constructions of their coils which can lead to different optimum power levels. I think the important thing to do when describing these is to highlight the resistance level, as I’ve noticed a decrease in the trend of using the word sub ohm and it could confuse vapers new to low resistance vaping.

  16. Mary a lynthacum

    I have been vaping since 2014-till now oct 2019. I now use no nicotine. In a few months i plan to stop vaping. Now that i have over come the nicotine. Please do not stop making flavors. I have not had any negative effects. With out vaping i would not have been able to stop smoking…

  17. What is the downside of using, say, 30 watts on a coil that is supposed to run at 70 watts. Asus sub ohm tank. It’s burning coils in a couple of days at 70. This is the first higher wattage tank I’ve used. Thanks!

  18. Hi. you explained it very well. I have some question about chart . Why green zone in all resistance is between 4 and 7 watt ? Is it dangerous vape 10 or 13 watt or bad for coil ? I built 1.8 ohm coil and as in the chart if i want to be in green zone i should set voltage 3 to 4 volt. Wire manufacturer recommends to set voltage on 5 and get 13 watt. As in the chart 13 watt is in red zone. I want to know how can i trust green zone. Thanks

    1. Hi Mahmood

      Thanks for leaving a comment. That chart was produced over 5 years, and our current recommendation is to follow the manufacturer’s guidelines. The exact materials in coils vary, and manufacturers should be able to give the best recommendations for coil usage.

  19. Hi James my name is Con I have a question my girlfriend vapes and she wants to know what watts does your battery need to be on mellow 4 so that the coil does not burn out?

    1. This depends on the resistance rating. Eleaf recommends 35 watts for a 0.3 Ω coil and 32 watts for a 0.5 Ω coil. You can also start low and work up until you get to a satisfactory vape.

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