๐พ Pets
Fish Tank Size Calculator
The old inch-per-gallon rule is a rough guide at best because it ignores the fish shape and the tank surface area. For goldfish and other heavy waste producers the realistic figure is closer to 5 gallons per inch of adult fish.
How it works
Small fish under 2 in
Medium fish 2-4 in
Large fish over 4 in
Fish type
Bottom dwellers (cory, pleco)
Total bioload
Minimum tank volume
Recommended volume
Filter turnover needed
Note
Frequently asked questions
How do I use the Fish Tank Size Calculator?
Fill in the fields above โ the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.