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How Long Does a Scuba Tank Last? Our Tank Duration Calculator Has the Answer

A question that many scuba divers ask themselves is: how long do scuba tanks actually last while diving? After all, running out of air while diving can be a terrifying experience. Unfortunately, it’s not a question that can be answered with a simple number.

There are certain determining factors that come into play but don’t worry, we’re here to help you dive into the details and figure it all out.

Average Duration of A Filled Scuba Tank While Diving

The length of time a scuba tank can last depends on several factors such as tank size, depth of the dive, breathing rate of the diver, and the type of diving activity being undertaken.

The most commonly used scuba tank size is the standard aluminum 80-cubic-foot tank, which can last anywhere from 30 minutes to 1 hour at a depth of 60 feet for an average diver to breathe normally.

For deeper dives, the pressure in the tank decreases faster due to the increased pressure of the water, which means the tank will last for a shorter amount of time. For example, a dive to 100 feet may only last 20-30 minutes on a standard tank.

Factors that Affect Scuba Tank Duration

There are several factors at play that determine the duration of your scuba tanks.


The deeper you dive, the more compressed the air in your tank becomes. This means that you will consume air at a faster rate than you would at shallower depths. As a rule of thumb, for every 10 meters (33 feet) of depth, the air consumption rate doubles.

Tank Size

The size of your scuba tank directly affects how much air it can hold. Smaller tanks will run out of air faster than larger tanks, all other factors being equal. The most common tank sizes are 80 cubic feet and 120 cubic feet.

Tank Size (in litres)Tank Size (in liters)
6 liters20-30 minutes
8 liters30-40 minutes
10 liters40-50 minutes
12 liters50-60 minutes
15 liters60-75 minutes

Please note that these are general estimates and can vary depending on individual factors such as diving depth, breathing rate, and physical exertion. It’s always best to plan your dive with a conservative approach and ensure you have enough air to safely return to the surface.

Diver’s Lung Capacity

A diver’s lung capacity affects the duration of the scuba tank as it determines how much air they can inhale with each breath. The larger the lung capacity, the more air the diver can take in, and the longer the tank will last.

Air Consumption Rate

A diver’s breathing rate also affects the duration of the scuba tank. The faster a diver breathes, the quicker the air supply will be depleted. SAC rate or Surface Air Consumption rate refers to how much air you breathe while on the surface. The higher your SAC rate, the more air you’ll consume, and the shorter your tank will last. This is why it is essential to learn proper air conservation while scuba diving.

To calculate your SAC rate, you need to measure the amount of air in your tank before and after a dive. The difference between the two measurements gives you the amount of air you consumed during the dive. Divide this number by the duration of your dive in minutes, and you’ll have your SAC rate.

How to Calculate Scuba Tank Duration

There are three ways to calculate scuba tank duration:

Applying the Rule of Thirds

The rule of thirds is a straightforward method of calculating how long your scuba tank will last. It involves using one-third of your air supply to descend, one-third to ascend, and one-third for emergencies and safety stops. Although this rule is generally meant for deep sea divers using helium-breathing mixtures and decompression divers, you can follow this rule at any depth to be absolutely safe.

Using Dive Computers

Dive computers are electronic devices that track your depth, time, and air consumption rate. They use this data to calculate how long your scuba tank will last based on your current diving conditions. Most dive computers have a feature that allows you to input your SAC rate and depth to calculate your remaining dive time.

Using Dive Tables

Dive tables are charts that provide guidelines for how long a scuba tank will last based on your depth and time underwater. They are useful for planning your dive and ensuring that you have enough air to return safely to the surface.

Using Our Scuba Tank Time Calculator

You can also use our custom and easy-to-use scuba tank air consumption rate calculator to get a more or less accurate estimate of how long your scuba tank can last underwater.

  1. Enter the Size of Your Scuba Tank

    First, enter the size of your scuba tank in cubic feet in the “Tank Size” field. You can typically find the tank size stamped on the tank or on a label.

  2. Enter the Current Pressure of Your Tank

    Next, enter the working pressure of your tank in psi in the “Tank Pressure” field. You can use a pressure gauge to determine the current pressure of your tank.

  3. Enter SAC Rate

    Enter your Surface Air Consumption Rate (SAC) in cubic feet per minute in the “Surface Air Consumption Rate (SAC)” field. This value can vary depending on your individual breathing rate and diving conditions.

  4. Click the “Calculate” button

    The duration result will appear below the form, showing you how long your scuba tank will last based on the information you provided.
    If you want to recalculate with different values, simply adjust the fields and click the “Calculate” button again.

Scuba Tank Duration Calculator


Several factors can affect the length of time a scuba tank lasts when diving. These factors include tank size, depth, breathing rate, tank pressure, water temperature, and diving experience.

By following the tips provided in this article, such as controlling your breathing, diving within your limits, and monitoring your depth and time, you can maximize your dive time and enjoy your underwater experience to the fullest.

William Dupre

William Dupre

Retired Master Diver with 20+ years of experience and 2100+ logged dives. Presently, spending my time blogging about Diving and checking off locations one by one from my bucket list of dive destinations.