Aquariums are available in a huge range of sizes and shapes and the options can be daunting to anyone new to the fish hobby.  With all these options, it can be easy to get lost and not know what size of tank will be appropriate for you.  I will list the most commonly found aquarium tank sizes and dimensions in the hopes that you can better choose which fish tank to buy.  All dimensions are in inches and in the format of Length x Width x Height.

A small aquarium tank would be in the range of 2 to 15 gallons.  These tanks are typically best suited to smaller community fish such as danios, some tetras, guppies, mollies, etc.  Single bettas will appreciate the extra space as well.

2.5 gallons - 12×6x8.
5.5 gallons - 16×8x10
10 gallons - 20×10x12
15 gallons - 24×12x12

Medium fish tanks range from 20 gallons to 40 gallons.  If you buy an aquarium tank in this range, you will have a wide variety of fish to display in it including cichlids, goldfish, plecos, and all sorts of common (and rare) community fish.

20 (long) - 30×12x12
29 gallons - 30×12x18
38 gallons - 36×12x20
40 gallons - 36×18x16

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Though an aquarium tank can be custom made in sizes of 500 gallons or more, I will consider the large fish tank range to be anywhere from 50 gallons to 150 gallons.  People can house such fish as oscars, piranhas and other “tankbuster” fish.

55 gallons - 48×13x20
75 gallons - 48×18x21
90 gallons - 48×18x24
120 (long) - 60×18x26
150 gallons - 72×18x24

As you can see, there are limitless options for common aquarium tank sizes.  There are also ones that come in “long” or “high” varieties meaning they are either longer or higher than a basic tank that holds the same volume of water.  Examples of uses include high tanks for seahorses or long tanks for arowanas.  If you are buying your first fish tank supplies and aquariums, many used options are available online and you can get great deals!