Fish Tank Volume Calculator
Enter the inside length, width and water height. Decorations and substrate reduce the usable volume a little.
Aquarium
Fish tank volume calculator
Enter the inside length, width and water height. Decorations and substrate reduce the usable volume a little.
—US gallons
US gallon = 231 cubic inches. Litre = 1000 cm³. Stocking still depends on species, filtration and maintenance — volume is only the first number.
Common questions
How do I calculate aquarium volume?
Multiply inside length × width × water height. Divide cubic inches by 231 for US gallons.
Should I fill to the rim?
Measure the actual water height. Substrate and a gap at the top reduce usable volume.
Does volume tell me how many fish I can keep?
It is only the first number. Species, filtration and maintenance matter more.