Fish Tank Size Calculator

A fish tank size calculator determines the minimum aquarium volume needed for a given number and size of fish. The classic "one inch of fish per gallon" rule is a starting point, but fish bioload, behaviour, and water filtration capacity all matter significantly

The calculator uses the standard published formula for fish tank size. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

This calculator works with centimetres, inches, gallons. You can enter values in the units shown — the calculator handles all conversions internally.

The calculator applies the standard formula for this type of calculation. See the 'How It Works' steps above for the detailed formula breakdown.