Stocking calculator

A rough sanity check, not a licence. It will tell you when you are clearly overstocked; it cannot tell you that you are definitely fine.

Tank length (cm)Tank width (cm)Tank height (cm)Adult fish length (cm)How many

Volume—

Surface area—

Stocking load—

Four things the number cannot tell you.

The inch-per-gallon rule is wrongIt ignores body mass, waste output and territory. A 10cm goldfish is not ten 1cm tetras.
Shoaling minimums come firstMost tetras and rasboras need eight or more. Six is not a shoal, it is six stressed fish.
Filtration is a floor, not a licenceA bigger filter lets you keep the same fish more safely. It does not let you keep more.
Footprint beats volumeA long shallow tank holds more active fish than a tall one of the same litres.