If you’ve been curious about the world of sub-ohm vaping there is a lot to learn. One of the most important elements you need to understand is Ohm’s Law. You may have already learned about Ohm’s Law when it came to wrapping your first coils, but it also plays an important part in keeping your device and batteries safe as you reach for more powerful builds.

Here’s a look at Ohm’s Law from the perspective of calculating amperage:

What are Amps?

Amps, or amperes, are used to measure the amount of current flowing through your device. As it relates to vaporizers, you want to know how many amps are being pulled from your batteries. This is because your batteries are rated up to a specific amperage, beyond which you could be drawing too much current, potentially damaging the battery.

It is good to know that you can find batteries in a wide range of amperage ratings. Generally, the higher the draw, the fewer milliamp Hours (mAh) you will get, while slower-draw batteries will give you larger mAh capacity. This is a tradeoff that you’ll have to get used to in working on your builds.

How to Calculate Amps - VaporFi

How to Calculate Vape Amps for the Best Experience

Whether you’re a seasoned vaper or a beginner, it is important to understand how to use your vaporizer in a safe manner by balancing the draw of the device with your battery rating. It’s important to be your own vape coil calculator. You may be wondering why it is necessary to use an equation that you learned in your high school physics lesson when vaping. Simply put, it will prevent you from damaging your batteries or worse still, causing your best vape pens to just die.

There needs to be a balance between how many draws your coils are exerting on the battery. If the draw is beyond the capacity of your current battery, it can lead to the draining and eventual damage of the battery itself. Proper balancing of the draw and battery capacity can allow you to achieve better and more powerful builds.

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Vape Mods and Drawing Capacity to Calculate Amps - VaporFi

Vape Mods and Drawing Capacity

Anytime you use a vape mod to vape, there is a certain amount of current that is drawn from the battery and into the coil. The coil then heats up your favorite e-juice and causes it to vaporize. There needs to be a delicate balance between how much current the coil is pulling from the battery. If the coil pulls too much current, it can eventually become damaged.

To determine this balance, the amount of current (amperage) needs to be determined for every mod. This is important so that you can select the right battery capacity for the best vape pens. Luckily, an easy way to calculate the amperes of the vaporizer exists in Ohm’s law (further discussed below).

There are 2 main types of mods that are used in vaping. Mechanical mods work in a truly manual design, where there is no resistance between the coil and the battery. This means that the draw of electric current (amperes) that is exerted by the coil is directly transferred to the battery.

On the other hand, regulated mods place a protective circuit between the battery and the coil. This protection limits the amount of draw that is exerted from the battery for safety purposes. In other words, it protects against overdrawing current from the battery and discharging it.

Calculating the amperes for mechanical and regulated vape mods is slightly different because of how they work. We’ll get into further details of the calculations below.

Using Ohm’s law to calculate Amps - VaporFi

Using Ohm’s law to Calculate Amps

Now that you understand the importance of matching the draw of electric current from the coil with the right capacity battery, we can proceed to show you how to calculate the right amps for your mod and best vape pens. Ohm’s law is a physical formula that is used to calculate various dimensions of an electric circuit. You can think of a vaporizer as an electric circuit in itself.

The formula is as follows: V = I x R


V = the voltage of the circuit (the intensity of the flow of electric current)

I = the amperage of the circuit (the rate of flow of electric current)

R = Resistance

During sub-ohm vaping, the total resistance in the circuit is normally less than 1 ohm. This means that the amount of resistance that is present in the circuit will have an effect on the total power a vaper gets when smoking.

With most modern day mods, you can increase the amperage of the device so that it draws more power from the battery. And as we can see from the formula, the higher the amperage, the higher the voltage.

With this ability to modify how much amperage you’re drawing, you need to get a battery that is capable of handling your needs and matching the draw from the coil. Let’s take an example of a coil that is rated at 0.8 ohms resistance and a voltage of 12 volts. From the formula, you will have:

12V = I x 0.8 Ohms.

To get the amperage, divide 12V/0.8 ohms = 15 Amps.

In this case, you will need a battery of 15 Amps or higher to match the maximum draw from the coil. It is always recommended to get a higher capacity battery (at least by 2A) so you have enough headroom on the amperage.

Regulated vs. Mechanical Mods

Before we can begin any discussion of how to calculate amps, we need to first clear up some confusion about regulated mods and mechanical mods. In a mechanical mod, there are no electronics standing between your coil and your battery. Thus, calculating amps is done by plugging your coil resistance and voltage directly into Ohm’s Law.

By contrast, a regulated mod includes some protective circuitry between the battery and coil. Thus, you are not using your actual coil resistance to determine your amperage. You are using a slightly different equation instead. This is because the regulator protects against overdrawing current and over discharging.

We will take a look at both methods below.

Mechanical Mods

Since this is the simplest to explain, we’ll get it out of the way quickly. Ohm’s Law is V = I x R where V is voltage, I is amperage and R is resistance. Using basic algebraic principles, you can easily plug in your voltage and divide by your coil resistance to get your amps.

For instance, if you are vaping at around 10.5V with a 0.5-ohm coil, you’re looking at 10.5/0.5 = 21A.

Now, check your battery. If it is rated at 21A or above, you’re good to go. If not, you need to find a battery with a higher amperage rating.

Calculating Regulated Mod Amperage

Alternatively, there is an extension of Ohm’s Law that includes power as measured by wattage. This equation looks like this: P = I x E. It’s easy to remember, because everybody loves “PIE.”

This is the equation that you will most likely be using to measure your amperage because the vast majority of vapers use regulated mods these days. They are safer and easier to use than mechanical mods for most new vapers.

Since a regulated mod has an electronic limiter in place between your coil and your battery, you do not need to worry about your coil resistance when calculating amps. The system will adjust itself to your coils instead to keep resistance stable. All you need to do is plug in your wattage and your minimum battery voltage.

You may choose to use the maximum wattage of your device for this purpose, or use the wattage that you will most commonly use if it is not the max wattage of your device. Divide the wattage by the number of batteries you are using. For instance, a 150W device with two batteries means you have a 75W load on each battery.

To determine your voltage you will need to figure out what the minimum voltage rating of your device is. Most of today’s devices have a minimum voltage of 3.2V per battery before they cut off. This is the protective circuitry in action.

Some companies publish the minimum voltage as the total voltage for all batteries, while others publish it as the minimum voltage per battery. If your manual says that the cutoff is 9V, but you have three batteries, you will know that the cutoff is actually 3V per battery. This is an important distinction to make.

So now that you have these two numbers, it’s time to plug them into your PIE equation. 75W = I x 3.2V. Once more, using basic algebra you can say that 75W/3.2V = 23.4375 amps.

Now, it is important to note that this is only a calculation of the amperage draw from the firing of your device. Since regulated devices also have passive hardware onboard you will need to account for up to 2A of extra draw on top of the number that you calculated. This will give you plenty of headroom just in case.

Why this Vape Wattage Calculation is Important

Simply put, matching the draw with the battery rating prevents the battery from venting. This refers to the tendency of the battery to release hot chemicals under high pressure, which can lead to many different hazards. This is especially true when building your own mods.

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Adhering to Battery Safety While Vaping - VaporFi

Adhering to Battery Safety While Vaping

It is important for all vapers, experienced or newbies, to adhere to safety guidelines when using their mods. This is because batteries are potentially dangerous items and they can cause damage if used incorrectly. In fact, this is the reason why this article is enlightening you about calculating amps in your vaporizers.

In addition to ensuring that you properly match your battery capacity with your electrical draw from the coil, there are other important safety precautions you should take. Make sure you handle the mod with care and only purchase batteries from authorized and reputable dealers such as VaporFi. It is also essential to use the right ohm coils for your device, especially when sub-ohm vaping. And finally, store your best vape pens safely, away from potential flammable materials.


At VaporFi, we know that once you understand how to calculate these numbers you will be well on your way to safely enjoying sub-ohm vaping. You will also have the tools necessary to choose the best possible batteries for your configuration.

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