40 Gallon Fish Tank Dimensions: Length, Width, Height & Weight

As an aquarium hobbyist, have you ever wondered if the dimensions of a 40 gallon fish tank are suitable for its inhabitants?

A standard 40 Gallon aquarium is often recommended for beginners as it is equally popular with experienced fishkeepers. Different species easily thrive in this environment which generally measures at 36 inches long, 13 inches wide, 20 inches high. Or:

Standard 40-gallon Tank Dimension = 30″L x 13″W x 20″H

The commercially available fish tanks come in various shapes, sizes, and even materials. Read on to find out more about 40 gallon fish tank dimensions.

40 Gallon Fish Tank Dimensions


Aquarium manufacturers commonly produce rectangular and square tanks while considering factors such as intended water content, whether freshwater or saltwater.

Each manufacturer has their own style and trademark when it comes to the fish tanks that they offer in the market.

With these things in mind, the 40 gallon dimensions, in terms of length, width, and height, varies accordingly as well.

Standard 40-gallon tank36 inches13 inches20 inches
40 gallon long aquarium48 inches12 inches16 inches
40-gallon Breeder tank36 inches18 inches16 inches

To know the size of a 40 gallon tank, you should determine the shape that you want first. For this article, we will focus on the most common aquarium shape.

Rectangle/Square Shaped Aquarium


Rectangular and Square tanks are the most popular aquariums for a reason. These tanks are affordable, easy to clean and manage, and fit well on any surface as they are usually designed to go against a wall.

Aquariums that are rectangular or square in shape are also the ones that are often recommended for new hobbyists. The larger surface area between the air and the water is best for overall fish health and better water quality.

It should be noted that these tanks must be placed on a sturdy stand or aquarium cabinet that can safely bear and accommodate the filled weight of the aquarium.

The fish tank sizes chart below shows the different measurements of a 40 gallon tank in IN (inches) and in CM (centimeters), from manufacturers Aqueon, Marineland, Sea Clear, and Aqua Dream.

Sea ClearAcrylicBreeder3691.441538.101640.64308.7837
Aqua DreamGlassTall2460.961435.562666.04317.1338

Here we can see that the 40 gallon tank length differs depending on the style that has been manufactured. The 40 gallon breeder tank dimensions, in terms of length, are usually 36 inches, while Tall or High tanks are measured only at 24 inches.

On the other hand, the 40 gallon tall aquarium, as the name suggests, has higher measurements when it comes to height. Compared with the breeder tanks with heights measuring only at 16 to 17 inches, the tall aquarium has a height of 26 inches.

Other Fish Tank Shapes


Unlike rectangular/square aquariums, some tanks are less readily available for purchase. There are manufacturers however, that create custom fish tanks for customers that provide the specifics of the style and how many inches they want the dimensions to be.

Other shapes that are seen for aquariums are as follows:

  • Bow front
  • Cylinder
  • ½ Cylinder
  • L-Shape
  • Angle L-Shape
  • Flat Back Hex
  • Hexagon
  • Triangle End
  • Multi Equal Side
  • Pentagon
  • Double Bullnose
  • Double Inverted Bow front
  • Flat Back
  • Radius Triangle
  • Triangle
  • Arch
  • Double Bubble
  • Bubble
  • Bullnose
  • Corner Bow front

Keep in mind that these shapes require different sizes that deviate from the standard measurements of the rectangular/square fish tanks.

If you opt to purchase any of these, make sure that the manufacturer knows you want the same capacity as a 40 gal long tank.

Frequently Asked Questions

How much does a 40 gallon fish tank weigh?

In case you’re wondering how heavy is a 40 gallon tank, the usual empty tank weight for a rectangular aquarium is 53 lbs. For breeder tanks, empty weight is 52 lbs., and for tall or high tanks, the empty weight measures at 50 lbs.

Glass or Acrylic Fish Tanks?

Aquariums can either be made from glass or acrylic. Glass is commonly used for aquariums that are shaped as rectangles, hexagons, bow front, and cylinders. Cost-wise, fish tanks made from glass are cheaper.

Now some shapes are harder to form using glass, and therefore acrylic comes into place. It is more malleable thus able to produce astonishing custom shaped tanks. Aquariums made from acrylic are also clearer and are more heat-resistant as compared to glass.

If you want an uncommon shape for your aquarium, then go for the ones made with acrylic.


Whether you are a new or experienced hobbyist, selecting a suitable aquarium can be a challenging task. Things like acquisition and maintenance cost, appropriate location, adequate space, and even fish species, must be considered when choosing a fish tank.

Hopefully, the 40 gallon fish tank dimensions discussed in this article can serve as your guide on what shape, size, style, and material you will choose to get, and which manufacturer you’ll purchase the aquarium from.