Tank Size Calculator
Plan your perfect aquarium with confidence. Add the fish you want — we'll tell you the tank size you need. Already have a tank? Use our stocking calculator instead.
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Add fish above to see your perfect tank size.
Add fish to calculate tank size.
Dream big, then plan
Most fishkeepers start with a tank and work backwards — picking fish to fit the space they already have. This calculator flips that. Start with your ideal setup: the species you want, the schools, the centrepiece. We'll tell you the tank size you need. No compromise before you've even begun. Once you know your target size, use our stocking calculator to refine the mix and check compatibility.
Disclaimer: Tank size estimates are conservative by design, based on bioload and fishkeeping experience. Experienced keepers with strong filtration and plants may exceed these; beginners may want to go larger. We have no affiliation with any tank, filter, or fish brands — this tool is built for hobbyists, by hobbyists.
Tank size calculator FAQs
What tank size do I need for my fish?
Add the fish species you want to keep to our tank size calculator. It uses bioload and fishkeeping experience to recommend a conservative tank size in litres or gallons. Start with your dream setup — we'll tell you the tank you need.
How does the tank size calculator work?
You add fish species and quantities to a wishlist. The calculator sums the recommended tank volume for each species based on bioload and fishkeeping experience. You can switch between litres and US gallons.
Is this tank size calculator free?
Yes. The tank size calculator is free to use with no sign-up required. It uses the same logic as leading fish tank apps.
Stocking calculator · How to use a stocking calculator · How many fish per gallon · Get the app