What Are the Dimensions of a 55 Gallon Fish Tank?

what are the dimensions of a 55 gallon fish tank

“What are the dimensions of a 55-gallon fish tank?” is a question many aquarists ask, and understandably so. After all, you will want to know if this behemoth aquarium will fit into your living space.

The standard 55-gallon fish tank dimensions are 48 inches long, 13 inches wide, and 20 inches high. However, it is worth noting that aquariums come in different styles and shapes, affecting their measurements.

Keep reading to learn more.

55 Gallon Aquarium Tank Dimensions


The standard 55-gallon tank dimensions are 13 inches in width, 20 inches in height, and 48 inches in length, assuming a rectangular shape.

These measurements require a minimum floor area of 624 square inches (or about 4.33 square feet if you prefer the dimensions in feet). If you need the sizes in cm (centimeters), the floor area is 4025.8 square centimeters.

It is worth noting that the term “gallon” denotes “volume,” which reflects the container’s water-holding capacity. It answers the question, how much water can the aquarium hold?

Not all 55-gallon aquariums have the dimensions mentioned above, considering these tanks may come in various sizes or be custom-built.

Fish Tank Dimensions Depending on Aquarium Type


Most rectangular fish tank sizes follow a more or less conventional standard measurement.

For example, a 36-gallon tank measures 30” long, 15” wide, and 21” high. Meanwhile, a 90-gallon aquarium might have a width, height, and length of 18”, 29”, and 48”, respectively.

Suppose you want a custom-built 55-gallon fish tank that measures 3 feet by 15 inches. In that case, the 55-gallon tall fish tank dimensions should be 36” long, 15” wide, and 24” high.

Bow-front aquariums can have different 55-gallon fish tank measurements from standard rectangular versions. The base might be rectangular, but the front section is semi-circular.

Sadly, the bow section can vary in design. Some have a half-cylinder style, while others feature a radius triangle. Bullnose bow-front aquariums are also different from double-inverted bow-front fish tanks.

These aquarium shapes or styles might have the same 55-gallon size, but their unconventional design makes measurements tricky.

The closest bow front dimension to a 55-gallon fish tank is 36.4” long, 16.4” wide, and 21.9” high. Again, don’t take these figures as absolute, as the design of the bowl section can change these measurements drastically.

How to Calculate Fish Tank Volume


Calculating fish tank volume (in gallons) is as straightforward as multiplying the aquarium’s physical dimensions in inches and dividing the product by 231.

Let us say you have an aquarium measuring 48” long, 13” wide, and 20” high.

48” x 13” x 20” = 13,104”

13,104 inches ÷ 231 = 54.02 gallons (or 55 gallons)

Suppose you have a fish tank measuring 48” long, 18” wide, and 21” high.

48” x 18” x 21” = 18,144”

18,144 inches ÷ 231 = 78.54 gallons or 80 gallons

Calculating 55-gallon bow front aquarium dimensions can be tricky because you must consider the bow segment’s central angle. The formula is as follows.

Bow front size = (LxWxH) + 0.5 x r2 x [α – sin(α)] x H

To calculate the “α” value, you need this formula.

α = 2π – 4β, where β is 0.5 x (L ÷ full W – W)

It is complicated, especially if you are unfamiliar with trigonometry. Hence, we recommend using an online fish tank calculator to determine 55-gallon aquarium dimensions with a bow front design.

What is the Average Weight of a 55-gallon Fish Tank?


Fish tank dimensions not only provide an estimate of how much water it can accommodate. It can also give you an idea of how hefty the aquarium can be.

The average 55-gallon fish tank weight is 78 pounds without water, fish, tank decorations, substrate, accessories, and other items. With everything loaded in, the aquarium can tip the scale at 625 pounds.

However, it is worth noting that fish tanks feature different materials, which can impact the aquarium’s weight.

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  • For instance, a 0.062-inch thick Plexiglass weighs about 0.38 pounds per square foot. Standard 55-gallon aquariums measure about 4.33 square feet, as mentioned above.


If we multiply 0.38 pounds by 4.33 square feet, we will get 1.6454 pounds.

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  • Thicker Plexiglass is heavier. For example, a 0.236-inch Plexiglass weighs 1.46 pounds per square foot, while a 0.94-inch-thick product tips the scale at 5.76 pounds per square foot.
  • Glass is heavier than Plexiglass. For instance, a 4-millimeter-thick (0.157 inches) glass can weigh 10 kilograms (22 pounds) per square meter (10.76 square feet).


Fish tank weight is crucial because you want a sturdy cabinet or aquarium stand for the 55-gallon fish tank. It will also help you determine how many helpers you need to lift the aquarium from its base.

The Number of Fish You Can Keep in a 55-Gallon Fish Tank


Just as the dimensions of a 55-gallon aquarium vary across types or tank designs, so do the number of fish you can keep.

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  • According to fish size


The general rule is to observe a 1:1 ratio – one-inch fish for every gallon of water. Hence, you can theoretically put 55 one-inch fish in a 55-gallon tank. You can also have a combination of fish species or sizes with this guideline.

For example, a 55-gallon fish tank can accommodate ten 2-inch goldfish (total = 20”), ten 1.5-inch Neon Tetras (total = 15”), and ten 2-inch Dwarf Gouramis (total = 20 “).

Unfortunately, your fish might be too tiny now, but they can become gigantic. For example, while goldfish average one to two inches, some can reach over a foot long.

Your 55-gallon fish tank might offer a suitable home for ten to twenty goldfish now, but what if they overgrow? Aquarists should plan their aquaponics system to account for the largest possible size for any given fish species.

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  • According to tank mate compatibility


Aquarists must also consider the fish’s nature and tank mate compatibility. For example, Neon tetras, guppies, Cherry barbs, danios, Harlequin rasboras, and bristlenose catfish are peace-loving community fish species.

However, some species are particularly territorial, so you may not be able to stick to the 1-gallon-per-inch guideline above. As an example, male betta fish are extremely territorial, so they’ll fight with other betta fish if the enclosure places them too close to one another.

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The answer to the question, what are the dimensions of a 55-gallon fish tank, is not a fixed one. Aquarium measurements vary depending on the fish tank type or design. Standard rectangular fish tanks measure 48 inches long, 20 inches tall, and 13 inches wide.

Meanwhile, a bow-front aquarium might have different dimensions, depending on the fish tank subtype. Cylindrical fish tanks and custom-built aquariums will also vary in measurements.

These fish tanks might vary in lengths, widths (or diameters), and heights, but they all hold 55 gallons of water.