Aquarium Volume & Stocking
Calculate an aquarium's water volume in litres and gallons, the weight of the filled tank and a rough fish stocking limit, free online.
About this calculator
Volume = length × width × height (cm³ ÷ 1000 = litres); fill to about 90% of the tank's internal volume. Water weighs 1 kg per litre, plus the tank and substrate. A simple stocking rule is 1 inch (2.5 cm) of adult fish per gallon (≈ 4 litres) of water, but filtration, species and behaviour matter more.