Calculate what volume your aquarium needs.
Enter the fish species, its approximate adult size and the number of fish, and find out the minimum recommended volume in the unit you prefer. No sign-up, no data stored.
Aquarium Volume Calculator
Standard Fishkeeping Formula
We apply the volume-per-centimeter-of-adult-fish ratio used by aquarists, in a neutral way.
Liters, US Gallons or UK Gallons
Choose the unit you prefer and get the result instantly.
Species Exceptions
We account for territorial or shoaling fish that need more space than usual.
No Sign-Up, No Waiting
The calculation happens in your browser. No accounts or passwords.
Space determines your fish’s wellbeing.
A tank that’s too small causes stress, poorer water quality and more illness, even if the fish seems to “fit” at first glance. The more room a fish has to swim and the more stable the water, the better its quality of life — which is why calculating the volume before buying, not after, usually avoids most problems.
What result do you get?
Before buying the tank:
Work out what size you need before choosing the tank, not after.
When adding a new fish:
Check whether your current tank has room for one more fish.
If you change species:
Verify whether your current tank is still suitable for the new species.
Frequently Asked Questions (FAQ)
Do I need to create an account?
No, never. You can use the calculator directly, with no sign-up or passwords.
What units can I see the result in?
You can choose between liters, US gallons and UK (imperial) gallons; the result is automatically converted to the unit you select.
Does the formula work for any fish?
The calculator uses a standard fishkeeping formula with exceptions for territorial or shoaling species, but it’s always a good idea to research the specific needs of the species you want to keep.
Is the result saved if I close the tab?
No. The calculation happens in your browser and disappears when you close or reload the page. If you want to keep it, you can write it down or take a screenshot.
Does this calculator replace a specialist’s advice?
No. It only calculates general guidance based on the data you enter. For specific questions about your tank, consult a specialized store or an aquatic veterinarian.