About
About Aquarium Calculator
We build free, accurate, no-nonsense calculators for fishkeepers — so planning a tank takes minutes, not spreadsheets.
Our mission
Aquarium Calculator exists to answer the everyday maths of fishkeeping in one clean, free place. Whether you're sizing your first nano tank or planning a large build, you should be able to get an instant, unit-aware answer without sign-ups, paywalls or clutter.
What we offer
The site brings together a full set of tools — tank volume, fish stocking, heater wattage, filtration and flow, substrate, water changes and tank weight — each working in your choice of litres, US or UK gallons, centimetres, inches or feet. Everything updates as you type and every result is shareable by link.
Accuracy you can check
We'd rather show our working than hand you a black box. Our stocking model uses a per-species bioload approach instead of the unreliable inch-per-gallon rule, and our constants are cross-checked against established references. Read the full methodology and sources .
Free and independent
Aquarium Calculator is independent and free to use. There's no app to install and nothing to pay. If you spot an error or have a feature you'd like to see, we'd genuinely like to hear from you.