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Aquarium Volume Calculator

aquarium volume calculator
PetFish101 Fish Tank Volume Calculator

With the use of this aquarium calculator, calculating the volume of a fish tank has never been simpler. All you need to do is enter your fish tank’s dimensions. Use this aquarium volume calculator to determine the precise amount of water needed to fill your recently purchased aquarium or the aquarium you are going to build by  yourself. Keep in mind that this method presupposes that your fish tank is empty and that there is no room for anything like substrata, driftwood, or pebbles. Choose from 8 common aquarium shapes, including a straightforward rectangular box, cylinder variations, bow front tanks, and more.

You can use petfish101 fish tank size calculator to estimate the proper tank population and whether you have enough room for the species you want to buy. Hence, you can keep more fish safely without overstocking if you know the amount of your tank with more accuracy.

Additionally, it’s crucial to know the size of your fish tank for a variety of reasons, such as: Knowing how to treat water with different chemical amounts, Understanding how frequently you should replace or re-fresh the water to keep your fish in good health. It’s crucial to get the medication dosage appropriate if you discover any ailments in your tank. The water capacity of your tank should be calculated as precisely as possible.

Moreover, knowing your tank’s water capacity is essential for determining when to perform water changes and tank maintenance.

If you have any questions about the formulae used to determine the size of an aquarium or how to use this tool, read the entire page.

How to use this tool as an aquarium gallon calculator

The easy techniques listed below will help you determine how much water your fish tank holds in gallons or liters.

  1. Select the aquarium’s shape.
  2. Enter the size of the tank.
  3. The volume of your tank is determined by the aquarium volume (in liters or gallons) calculator within seconds.

Note: As mentioned earlier, the fish tank volume calculator does not account for factors like the thickness of the glass or the volume of other objects like plants, fish, sand, gravel, driftwood, filters, and so on.

Estimating Aquarium Water Volume

Using the volume formula for your tank’s shape, you may calculate how much water it can contain. Although the procedure is the same for various tanks, the formulas vary slightly depending on the shape of the aquarium. e.g. rectangular, cylindrical, bow front, etc.

Rectangular Tank Formula

If the tank length, width and height is represented with l, w and h respectively the tank volume (v) is equal to l * w * h.

 v = l × w × h

Cylinder Tank Formula

If the cylinder tank radius and height are respectively r and h then we can find it’s volume (v) using the below formula;

v = π × r2 × h

Bow Front Tank Formula

If the tank length, width, full width and height are represented with l, w, fw, and h we can calculate the square area (m2/square meters) of the blow front tank as below;

m2 = l × w

and the elliptical area as below;

elliptical area = π × (l ÷ 2) × (fw – w) ÷ 2

Finally we can calculate the Bow Front Tank volume (v) as below;

v = (m2 + elliptical area) × h

Converting gallons to liters or liters to gallons?

There are two types of measurements you can take when you measurements your fish tank length, width or height. Those are imperial units (inch, feet) or metric units (millimeters, centimeters , meters). But to your comfort whatever the unit you may choose to enter you get the volume by both by liters (in metric units) and gallons (in imperial units). This is very important as most of the time the aquarium hobbyists like to refer to the gallons while others like to stick to metric units. The preferences vary by the country.

Read more about 75 gallon aquarium which is a popular size fish tank among aquarium hobbyists.


  1. How to make accurate measurements of my fish tank?

Try to measure your tank’s height to the water line rather than all the way up to the top while doing so. You should also measure from the top of any substrate layer that is present at the bottom of your tank.

2. Is glass thickness going to be a problem or not?

The thickness of the glass won’t really have a big impact on the volume estimate for the majority of residential fish tanks. To account for glass thickness, try to take your measurements from inside the tank.

3. What is the Aquarium Volume Calculator’s Overall Accuracy?

It’s pretty accurate, if you have taken the measurements carefully and accurate. There shouldn’t be any error except for the human error which might occur during the measurement pace. Therefore, you can obtain a reliable volume estimate if you carefully select the correct tank type and input accurate data into our aquarium volume calculators above.


The calculator shown above estimates your fish tank’s approximate water volume capacity. It is solely intended to be used as a reference for this use. Users use this tool at their own risk when treating tanks. Follow the manufacturer’s guidelines at all times, and take into account things like the aquarium’s contents (substrates, ornaments), water level, and glass thickness.