How Long Does The Air In a Scuba Tank Last? (With Examples)

The question sounds very simple, but however is quite complicated. The article is going to share profound insights regarding how long the air in the scuba tank last. Read on!

How Long Does The Air In a Scuba Tank Last? Based on various studies, an average diver, with an average tank, can last 40 to 60 minutes. The tank should be an 80-cubic-foot, and the depth should be 40 feet.
The other element regarding the diving industry is that it should be noted that the amount of air the diver consumes depends on the levels his or her of physical exertion. However, when it comes to how long the scuba tanks last various factors play a significant role.

How Long Does a Scuba Tank Last If You Dive Deep?

This is another complicated question, but if you’re a certified and qualified diver, you already know the thump rule, the deeper your dive, the higher the density of the air. Regarding the surface, the atmosphere’s pressure is 1 bar/ATA; the air has some weight, while water is 800 times denser than air. What does this mean?

How Long Does The Air In a Scuba Tank Last? With Examples

The analogy implies that water molecules are closer than air molecules. Therefore, under the water, pressure increases by 1 bar/ATA for every 33 feet/10 meters that you will go more in-depth. If you’re keen enough, you can see that you have to add 1 bar/ATA every time-depth increases by 33 feet/10 meters.

Therefore, to answer how long the scuba tank last in various depths, you need to know the relationship between density, pressure, and volume. It must be noted that pressure and volume are inversely proportional.

What does this mean? Take a look at this example;

If you fill a balloon with 13 liters of air at the surface, which is approximately 3.5 breaths, the balloon will be smaller when it gets under the water. But why does that happen? Pressure will cause the air inside the balloon to be much smaller. In other words, the air molecules will get closer to each other, making the balloon’s volume decrease. Meaning, your balloon will be twice smaller, which is 6.5 liters of air.
At 1 bar/ ATA for every 33 feet/10 meters, the balloon will be twice small; at 66feet/20 meters, it will be thrice smaller even though the air inside will be of the same quantity.

This example tells you that once you dive deep, your breath volume remains the same as that of the surface, but since air is denser beneath the water surface, there will be more air in every breath.

As for the scuba, its lasting not only depends on the maximum depth of the diver but also its dive profile.

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Diving Physics Example

If your favorite subject in school is not physics, worry not. Diving physics is not that involving. This a recreational summation is very easy and straightforward to understand. What is applied in this physics is Boyle’s Law, the law states a linear relationship between volume, depth, density, and pressure.

Here’s a quick example of Boyle’s Law at 30 meters:


3 bar



The standard means that at the center of 30m, at the pressure of 3 bars, the thickness of air is thrice dense. Therefore, to fill the lungs with the same volume at a depth of 30m, the air quantity should be three times that of the regular surface.

In other words, the deeper you go, the more pressure, the more gas you will use. And that is how diving physics work.

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Factors That Determine How Long The Scuba Tank Will Last

The tank’s volume

One of the most common pillars in as far as the scuba tank is concerned is tank volume. In most cases, the standard tanks are 80-cubic-foot aluminum tank, and it holds 80-cubic of air if is compressed at 3000 pounds per square inch. However, there are different sizes of scuba tanks that are made of other materials apart from aluminum.

Therefore, if you’re after a long or deep dive, you’re advised to choose tanks with the greater internal volume. And if you’re a petite diver, little air is enough for you, and you should select smaller tanks. If other factors are kept constant, the large the tank’s volume, the longer it lasts.

The breathing rate

This one is unique, but the more breaths under the water, the faster the tank will get empty. Therefore, if you want the tank to last longer, you should breathe slowly for your tank to last longer. To achieve this, you should exhale long enough to clear the carbon dioxide from dead air space since this is what triggers the breathing urge.

Carbon dioxide is one of the waste gases, and your body needs to get rid of it. Hence, the brain creates the urge to breathe once it senses that carbon dioxide is above the required levels.
The rule of the thump, ensure you exhale long enough to flush out carbon dioxide. I do so; you will delay the urge to breathe.

Lung capacity

By nature, we are not equal in everything that applies to the lungs. Naturally, a considerable body mass implies huge lung capacity or volume, and a small body mass stipulates that it has a small lung capacity.

Lung capacity plays a significant role in terms of air consumption. This is because the smaller divers use smaller air than bigger divers. But why is that? The answer is straightforward; big divers need more air every time they breathe to fill the large lungs.

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How To Calculate Air Consumption Rate?

You can accurately calculate air consumption of various depths using Boyle’s Law and the diver’s SAC rate (Surface Air Consumption rate). In this, you should use the 47 meters’ example; you need to figure out how long the scuba lasts on the surface and how long it will last at 47 meters.
For easier understanding, the example uses a full tank of 80-cubic-foot tank placed at the surface for 3 hours. Next, use the density at 47 meters, which is 5.7, to calculate the air consumption rate at that depth.

180 minutes / 5.7 density = 31 minutes (the air in a scuba tank last)

Tips for improving the air consumption rate:

• Relax both yourself and breathing

• Avoid using your arms for swimming

• Be slow in your movement

• Breath out longer than when you breathe in

• Be constant with your speed

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What Are The Other Factors That Can Limit Your Driving Time?

In everything, the air in a scuba tank is paramount for your diving expeditions. But also other factors that can limit your diving time. This includes temperature, and if your diving crew is being faster in their diving than you, you will consume more air, which will limit your diving time.

Final Thoughts

When it comes to How Long Does The Air In a Scuba Tank Last? (With Examples), various factors determine the outcome. Knowing how long it will last, you must be well acquainted with water pressure physics, air consumption rates, and tank volumes.
As a diver, you should also learn how to control your breathing rate. This is because the more you breathe, the more you will diminish the content of your tank. Ensure you breathe slowly for the tank to last longer.
Finally, the experience matters. A professional diver knows all the aspects that will make the tank to last longer than an entrant. If you’re a beginner, you’re advised to join experienced divers; you’ll learn more. Enjoy yourself! We hope that you have found this article beneficial and that we have answered the question; How Long Does The Air In a Scuba Tank Last? (With Examples)


Hi, I’m John who owns multiple different boats and i love all kinds of water activities. From boating to fishing, from scuba diving to windsurfing, from water tubing to snow tubing.

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