A Cheat Sheet to Fish Tank Gallon Sizes and Dimensions

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Are you in need of an overview chart that’s referencing the sizes and dimensions of all fish tanks? You may want to bookmark this page.

Fish Tank Measurements With Standard Shapes

Firstly I will be listing the dimensions and gallon capacities of the most popular aquariums with a standard rectangular shape.

After that, I will list the branded tanks with irregular shapes and sizes.

Here are the dimensions and gallon sizes of all standard fish tanks:

Small Standard Aquariums

You’d want to avoid getting a small tank if you’re a complete beginner in fish keeping.

Smaller tanks get polluted the quickest and it’s more difficult for a beginner to keep the water parameters in check.

Mid-Sized Standard Aquariums

If you’re a fish keeping beginner you’d want to start with a mid-sized tank as it’d be easier to manage.

I realize we all may have space and budget constraints but if you have the means to – go for a middle-sized aquarium.

Large Standard Aquariums

Large tanks can be very rewarding if you do your homework.

Nothing compares to having a big ecosystem with lots of small schooling fish, turtles or monster fish at home.

Larger aquariums are also the most stable in terms of water parameters.

Measurements of Brand Fish Tanks With Irregular Shapes and Sizes

Branded tanks don’t follow any rules about dimensions or gallon capacities.

They are mostly unique and the brand that makes the tank decides what its measurements would be.

Here are the dimensions of all irregularly-shaped aquarium kits:

Small Branded Aquariums

Starting with the dimensions of the smallest branded tanks, this is probably the longest chart in this list.

That’s because many brands recognize that small tanks are the biggest revenue drivers (which is not a good thing, since as I said earlier, beginners should ideally start with a mid-sized tank).

Mid-Sized Branded Aquariums

The mid-sized branded tanks can also be good for starters in the hobby, as long as they are not too weirdly-shaped.

Large Branded Aquariums

And finally, here are the dimensions of large branded tanks that have irregular shapes.

How to Calculate the Weight of Your Aquarium?

To calculate the total weight of an aquarium you’d want to first figure out how much it weighs empty.

After that, you calculate the water weight and then add the two together. To find out how much your tank weighs follow these steps:

1. Calculate the surface area of the fish tank.

   To find the total surface area of your tank you’d need to find the surface areas of each of its walls, including the bottom, and add them together.

   The surface area of each rectangular flat surface is calculated by multiplying its sides.

   So if your tank’s wall measures 10 x 20 inches, then you multiply that and get that the surface area of that wall is 200 square inches.

   Do this for each of the tank’s flat surfaces and add them together.

   The formula for finding the surface area for a standard rectangular tank is:

   (2 × length × height) for the sides + (2 × width × height) for the other two sides + (width × length) for the bottom.

   Bowfront tanks are an exception to this formula because they have a curved wall which is almost impossible to calculate on your own at home.

2. Calculate the empty weight of your tank.

   To calculate the empty weight of a tank you’d want to multiply its total surface area by the thickness of the walls.

   The material your tank is made of plays a role here since different materials have different weights.

   Typically aquariums are made of acrylic or glass. Glass weighs roughly 0.5165 pounds per square foot for each millimeter of thickness.

   Acrylic weighs approximately 0.24 pounds per square foot for each millimeter of thickness.

   Measure the thickness of the tank’s walls in millimeters and write that down.

   To proceed with calculating the tank’s empty weight you’d want to convert the square inches of total surface area we found in step 1 into square feet.

   This is easily done by dividing the total square inches by 144 since there are 144 sq inches in an sq foot.

   After you convert the surface area of the fish tank in square feet multiply that by the thickness of the glass in millimeters and the specific weight of the material.

   The formula looks like this:

   Tank Surface Area in Square Feet × Thickness of the Wall in mm × Specific Material Weight.

   For example, if your tank has 7 square feet of surface area, with a wall thickness of 10 mm, and is made of glass the calculation would be 7 × 10 × 0.5165 = 36.155 pounds of empty weight.

3. Calculate the gallon capacity of the tank.

   All tanks that you buy from the store will have a label clearly stating how much water they can hold.

   However, if you get a second-hand tank or have just forgotten what it was there is a way to calculate that.

   You simply need to convert the tank’s height, length, and width from inches to feet, then multiply them to find out the volume in inches.

   Turn that into cubic feet and multiply the result by 7.48. To convert the cubic inches into cubic feet you need to divide the volume by 1728.

   If this seems counterintuitive thank the Imperial unit system.

   Taking this into account you can use the following formula to calculate the gallon capacity of your tank:

   (Lenght × Width × Height, all in inches) ÷ 1728 x 7.48

   So if you have a tank that measures 10 × 20 × 15 inches and you’re going to fill it with fresh water, then the calculation would look like this:

   ((10 × 20 × 15) ÷ 1728) × 7.48 = roughly 13 gallons.

4. Calculate the filled weight of the tank.

   To do so you’d want to first find the weight of water and then add that up to the empty tank weight.

   To calculate the weight of water:

   Multiply the gallon capacity of your tank, which we found in step 3 by how much water weighs per pound.

   Freshwater and saltwater have different weights because of their different density.

   Freshwater weighs 8.345 pounds per gallon. Saltwater is heavier and weighs about 8.554 pounds per gallon.

   So if your tank can hold 20 gallons and you want to fill it with freshwater then multiply 20 × 8.345 = 166.9 pounds.

   Now add that up to the tank’s empty weight (calculated in step 2) and you’d find the total weight of your tank when it’s filled to the brim with water.

I provided all the formulas so that anyone with a non-standard tank can figure it out on their own.

For a generic weight estimate of standard tanks you can use a fish tank weight calculator like this one.

Getting equipment according to the dimensions of the aquarium?

Selecting aquarium equipment based on the size of the tank is essential for its long-term success.

Lighting

The dimensions of a fish tank play a huge role in the choice of aquarium lighting because light itself has a limited water penetration.

If you’re in the middle of your research on choosing a suitable light fixture for your aquarium plants you can check my guide on that here.

In that link, I do specific product recommendations based on aquarium depth and the type of plants you may want to keep.

The same rules apply for picking adequate grow lights for saltwater reef aquariums.

Corals are very sensitive to the intensity and spectrum of the incoming light they use for photosynthesis.

To end up with the right LED light you’ll need to take into account the dimensions of your coral reef aquarium.

There are stronger units that penetrate the water well and are suitable for deeper reef tanks and others that are less intense, making a good addition to aquariums with less demanding corals.

I made specific recommendations on choosing the best LED lights for corals based on aquarium height and the species you want to keep. Visit the link to learn more.

Filter

Choosing the flow rate of a water filter should also be made in conjunction with the gallon capacity of the fish tank.

If you keep larger carnivorous fish that produce more waste or you plan to overstock the tank you’d want a stronger filter that turns the water at least 6 times per hour.

For Oscar or Cichlid fish tanks getting an external canister filter makes perfect sense as these units produce more flow and have enormous space for media, which in turn keeps the aquarium clean and safe.

I have an article on choosing one according to your aquarium’s gallon capacity (visit the link to learn how to make a choice).

If you want to keep aquatic turtles you should still take into consideration the available water volume in the aquarium.

In this case, you can check my article on picking a good filter for a turtle aquarium according to gallon capacity.

Turtles are messier than most aquatic pets and require a water turn over of at least 8 times the whole aquarium’s gallon capacity per hour.

Heater

A small 3-gallon, 5-gallon, or 10-gallon tank with tropical fish requires a small-sized aquarium heater that’s ideally under 6.5 inches in length.

I’ve seen enough small aquariums with a spoiled interior because the owner got an over-sized heater.

Wavemaker

Last but not least, the gallon capacity of your reef tank, for example, plays a major role in your choice of aquarium wavemaker.

You can check my guide on how to make the correct choice by clicking here.

Knowing the exact dimensions of your new fish tank will give you the needed information to make adequate decisions on choosing livestock and the purchase of equipment.

Drop me a comment below if you have any questions in those areas and I will answer as soon as I see it.

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