Aquarium Calculator

Determining fish tank volume has never been easier – with this aquarium calculator, you can do it in a blink of an eye. Find water volume 💧 which will fill up your container: choose between 7 typical aquarium shapes – from a simple box, through cylindrical variations, to bow front tanks.

If you're wondering what the formulas are to calculate an aquarium's size or you're not sure how to use this tool, just scroll down, and you'll find the answer below.

If you're looking for the amount of water that goes into a swimming pool, check out our pool calculator. We also have a pond calculator if you're interested in backyard ponds.

In our aquarium calculator, we implemented seven popular fish tank shapes:

If you want to calculate the aquarium size manually, you can use the different formulas for volume, depending on the tank shape.

Rectangular prism

To find the volume of a standard aquarium, calculate the volume of a rectangular prism (also called the volume of a box):

rectangular = height × width × length

Our rectangular prism calculator will make this calculation simple.

Cube

The cube-shaped aquarium has the easiest volume equation – simply raise the edge length to the third power:

cube = length³

Our cube calculator can help you calculate this volume easily.

Cylinder and its fractions

If you want to calculate the water volume of a cylindrical aquarium, use the formula for cylinder volume:

cylinder = π × (diameter / 2)² × height

Your fish tank is a half-cylinder? No problem, just divide the formula above by 2:

half cylinder = π × (diameter / 2)² × height / 2

To determine the volume of the quarter of the cylinder, take a fourth part of the full volume:

quarter cylinder = π × radius² × height / 4

It's handier to use radius instead of diameter in this last case: diameter = 2 × radius.

Bow front and bow front corner aquarium

Calculating the volume of the bowfront aquarium is a bit trickier. You need to have given four dimensions: height, width, length, and the full width of the aquarium, and then you can derive the final formula:

bowfront = height × width × length + 0.5 × r² × (α - sin(α)) × height,

where α is the central angle of the circular segment, in radians, and r is a radius of a circle. You can calculate the angle α with α = 2π - 4β, where β is an angle expressed as:

tan(β) = 0.5 × length / (full_width - width).

For the aquarium with a bow front intended to stand in the corner, the formula is:

corner bowfront = (0.5r² × (α - sin(α)) × height)/2

Is your aquarium in a custom or bizarre shape? Check out our other tools, such as the triangular prism volume or spherical cap calculator, which can find water volume for spherical aquariums, also called fish bowls. Just remember that such tanks are not appropriate for keeping fish, and in some countries, they're even forbidden!

Spherical aquariums are usually small tanks, fish have to swim in circles, which is unnatural for them, and it's hard to put a filter into such a tank. Consider a different aquarium shape despite the fancy look of such a tank.

If you want to calculate how many gallons of water your tank contains, follow these simple steps:

1. Choose the shape of your aquarium. Assume that you have a bow-front fish tank, so select this option from a drop-down list.

2. Enter the tank dimensions. In our case, we need to type four values. Let's say that the length is 35 in, full width – 18 in, width – 15 in, and height – 20 in.

3. The aquarium calculator finds the volume of your tank. In our case, it's 51.55 gallons.

4. If you're wondering how much that is in liters, click on the unit name and select the one you're interested in – e.g., our aquarium volume in liters is 195.14.

Remember that those calculations may serve as estimations, and the result obtained doesn't mean that precisely 51.55 gallons will fit into your tank. We don't take into account, e.g., the thickness of the glass or the volume of other objects, such as sand, gravel, filter, plants, and... fish. Also, you don't fill up your container completely, do you?

You heard that your friend has just bought a 75-gallon aquarium. Well, it's hard to imagine how big that is. Let's check it with this aquarium calculator!

1. Choose the fish tank shape. We know that our friend is rather a traditionalist, so his obvious choice is a standard rectangular prism tank.

2. Type in the volume – in our case, put 75 gallons into the volume box.

   As the given volume may be a result of an infinite combination of the rectangular prism dimensions, we need to input more information.

3. Enter two tank dimensions. The usual height of the aquarium is something between 18-26 inches; let's say it's 22 inches. Additionally, assume the width is the same as the height.

4. We found out that this 75-gallon aquarium has ~35.8 in length, so the dimensions are 35.8 x 22 in x 22 in. Quite big, huh? Experiment with different dimensions and shapes to get a better understanding of the concept of volume.