Aquarium calculators for every number your fish tank needs.
Free calculators for tank volume, stocking, heaters, filters and water changes. Each one shows its working, in gallons and liters. Start with your tank's size:
This tank holds 56.7 US gal (215 L) to the brim, but about 45.9 US gal (174 L) of water once the glass, a 1 in gap, 2 in of substrate and the decor are taken off. That is 19% less. Use the real figure for heaters, water treatments and stocking.
- Also
- 174 L · 38.2 UK gal of water
- Inside volume, brim-full
- 53.5 US gal (203 L)
- The glass takes
- 3.2 US gal (12.1 L) (6 mm walls)
- Weight of the water
- 383 lb (174 kg)
- Rocks, wood and equipment take
- 1.9 US gal (7.2 L) (4%)
- Footprint
- 624 sq in (4.33 sq ft)
Then work out
How big is it, and what does it need?
Size the tank and the equipment that goes with it.
- VolumeGallons, liters, real water volume, water weightOpen calculator
- DimensionsStandard tank sizes that match, footprintOpen calculator
- HeaterWatts, one heater or twoOpen calculator
- FilterTurnover rate, GPH and L/h rangeOpen calculator
- SubstratePounds, kilograms, liters and bagsOpen calculator
- WeightTotal filled weight, floor loadOpen calculator
- Glass thicknessMinimum glass thickness for each panelOpen calculator
- Running costCost per month and year, by equipmentOpen calculator
What can live in it, and how do I keep the water right?
Plan the fish, then the routine that keeps them healthy.
Already know your tank size?
Tap your tank. Its real water volume, weight, heater, filter, gravel and fish numbers are worked out for you.
Look up a fish
How big it grows, the tank it needs, how many to keep and who it can live with.
Guides
The reasoning behind the numbers, in plain language.
- How to Set Up Your First Aquarium, Step by Step
Tank size, equipment, cycling and first fish, in order, with the numbers for each step.
- What Size Fish Tank Should I Get?
Which size suits which fish, what long, high and breeder mean, and what to check before you buy.
- How Many Fish Can I Put in My Tank?
The rules that decide it, and checked example lists for five common tank sizes.
- The Aquarium Nitrogen Cycle, Explained
What happens in the filter, the fishless method day by day, and how to read your tests.
- Aquarium Heater Size Guide
Wattage chart for every standard tank in warm, normal and cold rooms.
- How Many Gallons Is My Fish Tank?
Three easy ways to find the size of a tank with no label, with a chart to match it to a standard size.
- How Much Does a Fish Tank Weigh?
Empty and filled weight of every standard tank, and how to tell if your stand and floor can carry it.
- How Often Should You Change Aquarium Water?
The simple weekly rule, a chart by tank type, and a safe step-by-step method.
Why trust these numbers
The working is shown
Every calculator page gives the formula, a worked example and the source of each rule of thumb. Nothing is a black box.
Tested before release
Each formula is checked against published examples and manufacturers' figures. How we calculate
Real water, not label size
A "55-gallon" tank holds about 46 gallons of water. We work from what is really in the tank, because that is what the fish live in.
Independent
Not owned by any aquarium brand or shop. No sign-up, and your numbers stay in your browser. About us