AquariumCalcs: Fin & Figures — for the fish aficionado
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Fish Tank Dimensions & Size Chart Calculator

Standard aquarium dimensions by gallon, from a 5 gallon nano to a 150 gallon showpiece — plus a lookup tool if you already know your gallon size and just need the inches.

Your numbers
48 × 13 × 21 in
Standard 55 gallon aquarium — the most common "starter big tank" size.
SizeDimensions (L × W × H)Weight, filled

Common sizes, in detail

Check footprint, not just the gallon number

Two tanks with the same gallon rating can have very different footprints — always check the actual floor footprint against your furniture, not just the gallon number.

Source: Standard tank dimensions are the sizes published by major aquarium tank manufacturers (e.g. Aqueon, Marineland) for their standard glass tank lines.

Frequently asked questions

What are the dimensions of a 20 gallon long tank?

A standard 20 gallon long is 30 × 12 × 12 in — longer and shallower than a 20 gallon high, which makes it a better footprint for bottom-dwelling and active swimming fish.

What's the difference between a 20 gallon high and a 20 gallon long?

Both hold 20 gallons, but a 20 gallon high (24 × 12 × 16 in) is taller and narrower, while a 20 gallon long (30 × 12 × 12 in) is longer and shorter — the long is generally the better stocking footprint.

How much does a 55 gallon tank weigh full?

Around 625 lb filled, plus roughly 78 lb for the empty tank itself — always confirm your stand or floor can support the total before filling. Use the Tank Weight and Stand & Floor Load calculators to check your specific setup.

More Tank Setup & Sizing calculators

Aquarium Glass Thickness Calculator Aquarium Substrate Calculator Stand & Floor Load Calculator

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