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You don’t need to be good at maths to calculate how much water your fish tank can hold. Just grab a tape measure and a calculator and I’ll show you an easy way to work it out.
To work out how many litres of water your aquarium can hold you need to measure its dimensions in centimetres. Then calculate the length x width x height. Then you divide the answer by 1000. The answer after dividing will give you a fairly accurate litre capacity for your fish tank. This method works best for rectangular and square/cube aquariums.
If you would like to know how to get a more accurate calculation of litre capacity, or what other things you need to consider when doing the maths, I’ve got some information and tips to help you.
How To Get A More Accurate Calculation For Aquarium Water Volume – Rectangular/Square/Cube Tanks
The method above will tell you how many total litres (approximately) your tank can hold. If you would like a more accurate calculation there’s a couple of points to consider.
- Measure To The Fill Line – Measure the height to the line/level that you will be filling the tank to, rather than the upper edge.
- Measure Internally – If the tank is large enough for you to get a tape measure and your hands into it take your measurements from the inside of the tank. That way you won’t be including the dimensions of the outer glass in your calculations.
Tip: Whether you measure your fish tank externally or internally the litre capacity calculation is for a completely empty tank. Adding items and livestock to the tank reduces the amount of water that the tank can hold.
Tank Water Displacement By Gravel And Tank Decor Etc
All items added to a fish tank will displace water because they take up some of the water space. Which means that the water volume in your fish tank will be reduced in line with the amount of gravel, plants and fish etc that are in in the tank. Unfortunately, calculating the loss of water volume can be difficult to do if you don’t know the exact displacement value of every item in your tank. Also, plants grow and fish keepers often change the decor and tank inhabitants from time to time, which changes the displacement value of the tank’s contents.
This means that you have to use your own judgement on this unless you like doing some serious maths. It’s a case of using your knowledge of the aquarium alongside your best mathematical judgement. Your calculations are unlikely to be spot-on but they should give you a good idea of the water volume nonetheless.
Is It Important To Know How Many Litres Of Water Are In Your Fish Tank?
It’s important to know at least a close approximation of how many litres of water your fish tank is holding once it’s up and running. I know it can be difficult to calculate the exact number but having a good idea of the water volume is useful for several reasons.
Here’s some of the reasons why knowing how much water your aquarium contains is helpful.
- Stocking Your Tank – Knowing how much water your tank can hold, or is holding, helps you to judge how many/types of fish, shrimp and snails you can keep.
- Medication – If your fish become ill and you need to medicate them the dosage used is normally measured on how many litres/gallons of water the tank contains. So getting your calculation of water quantity as close as possible is important.
- Tank Maintenance – Tank maintenance involves water changes. Whether these are small regular water changes, or larger full tank maintenance ones, they’re important for keeping your tank healthy. Knowing how much water your tank holds helps you to judge the percentage of water you will be changing. This is particularly important when it comes to fish or shrimp that can only tolerate small changes in water parameters.
- Tank Filtration – Most fish tanks benefit from being filtered. And no matter what type of filtration system you choose the filter needs to be able to cope with the water volume in the tank. So it’s important to know how much water your tank holds, or will hold, before you buy your filter.
Interesting Fact: 1 Litre of water weighs 1 Kilogram. Which makes even a small fish tank pretty heavy
My Tank Isn’t Rectangular/Square/Cube So How Do I Measure The Water Volume?
Not all tanks are rectangular/square/cube. Aquariums come in all different shapes and sizes. For example, you can buy bow fronted, panoramic, cylindrical and even hexagonal tanks. Calculating the water volume of these tanks involves a little more mathematical know-how. Fortunately there are website calculators available that will do the more difficult maths for you.
I came across a website that calculates all sorts of mathematical problems for you. There’s a section for calculating aquarium volume for tanks of different shapes and dimensions that’s really helpful.
Here’s the link: https://www.omnicalculator.com/other/aquarium-volume
So, if like me, maths isn’t your strong point grab a tape measure and use the omnicalculator tool.
