Simply Aquarium  Aquarium Volume Calculator
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How can you accurately find the volume of water in your tank? A good aquarium volume calculator should match the shape and account for any objects in your tank.
I’ve had lots of different tanks over the years, and while figuring out the water volume in a rectangular tank is straight forward it can be difficult with other tank shapes. An aquarium volume calculator can make life a lot easier if you have a bow front tank for example.
Many aquarium volume calculators online have a good range of shapes but crucially lack the ability to account for any objects you have in your tank. I set out to change that.
So if you want to get an accurate estimate for the water volume in your aquarium, whether straight lined, curved, or corner tank, then read on to find out how!
Why Might I Need To Know The Volume Of My Tank?
There are a couple of very good reasons why you might need to know the water volume of your aquarium:
 Understanding the dosage levels needed for medication. If you encounter any diseases in your tank it’s very important to get the dosage for medication right. The more accurately you can calculate the water volume in your tank the better.
 Stocking levels. The more accurately you know your tank’s volume the more aware you can be of how many fish you can keep safely without overstocking.
 Water maintenance and changes. Knowing the water volume of your tank is a key factor to help drive when to do your water changes and tank maintenance.
How Can I Make My Measurements More Accurate?
 Measure to the fill line! When measuring the height of your tank try to measure to the water line rather than all the way to the top of the tank. If you have a layer of substrate at the bottom of your tank you should also measure from the top of that layer.
 What about glass thickness? For most domestic tanks, the thickness of the glass won’t really have a great effect on the volume calculation. But do try to take your measurements from inside the tank to account for glass thickness.
 The sides of my aquarium are tapered! If your tank has tapered sides try to take width measurements at the mid distance between the water line and the top of the substrate.
How Does The Aquarium Volume Calculator Account For Tank Objects?
Our aquarium volume calculator allows you to enter an overall weight for the objects in your tank. This is subtracted from the initial volume to give the final volume.
We do this by using the following factors for imperial and metric:
So depending on whether you enter in pounds or grams we either multiply by 0.12 or .0001 before removing this result from the initial volume.
What Are The Formulas Used In The Aquarium Calculator?
If you want to check calculations manually, or understand more about how our aquarium volume calculator works you can find the formulas for all of them below.
But notice that all of them give the cubic volume (volume³). To find the volume in US gallons or liters we use the following factors:
So to give the volume in US gallons we divide the cubic volume (in³) by 231. To find the volume in liters we divide cubic centimeters (cm³) by 1000.
Formulas For Tanks With Straight Lines
 Rectangular Prism or Cube:
 Volume³ = length * width * height [5]
 Hexagonal Tank:
 Volume³ = ((3*√3)/2) * front width² * height [6]


 This is for a regular hexagon, so each side panel must be the same size.

 Flat Back Hexagon:
 Volume³ = (((((3*√3)/2) * front width²)/2) + (side * length)) * height


 This uses the formula for a regular hexagon but divides by two to give the front section. The back section uses the formula for a rectangular prism.

 Octagonal Tank:


 Again, this is for a regular octagon. Each side panel must be the same size.

 LShaped Tank:
 Volume³ = ((length 1 * width 1) + ((length 2 – width 1) * width 2)) * height

 This calculation splits the L shape into two rectangles to calculate their areas. It then adds them together before multiplying by the height.
Formulas For Tanks With Curves
 Bow Front Tank:
 Volume³ = (((𝛑 * (length/2) * (full width – width))/2) + (length * width)) * height


 This calculation uses the formula for half an ellipse for the bow front [7], along with a rectangular prism at the back.

 Cylindrical Tank:
 Volume³ = (𝛑 * radius²) * height [9]


 To make things easier to measure, we ask you to include the full diameter and our calculator divides it by two to get the radius.

 Half Cylinder Tank:
 Volume³ = ((𝛑 * radius²) * height) / 2


 This is exactly the same as the cylinder, but with a simple divide by two to get the half cylinder!

 Elliptical Tank:
 Volume³ = 𝛑 * radius 1 * radius 2 * height [10]
 Double Bullnose Tank:
 Volume³ = ((𝛑 * (width/2) * ((full length – length)/2)) + (length * width)) * height

 This is very similar to the calculation for a bow front tank. But here we use the formula for a full ellipse to account for each curved end of the tank.
Formulas For Corner Tanks
 Corner Cylinder Tank:
 Volume³ = ((𝛑 * radius²) * height) / 4


 This is simply the formula to calculate the volume of a cylindrical tank but divided by four.

 Corner PentagonTank:
 Volume³ = (length² – ((length – end pane)² /2)) * height
 Corner Prism Tank:
 Volume³ = ((length 1 * length 2)/2) * height [11]


 This formula calculates the area of a triangle before multiplying by the height.

 Fishbowl Or Spherical Tank:
 Volume³ = (4/3) * 𝛑 * radius³ [12]

 Again, to make things easier to measure, we ask you to include the full diameter and our calculator divides it by two to get the radius.
How Accurate Is The Aquarium Volume Calculator Overall?
If you choose your tank shape carefully you will be able to get a good volume estimate. You can increase the accuracy by including the weight of any objects in your tank.
But you should note that this is still an estimate. If you are using this as a guide for any treatments for your tank ensure you follow the product manufacturer’s instructions carefully.
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