TankStockingAquarium Volume Calculator
Find out how many gallons and litres your tank really holds — for any common shape — then send the result straight to the stocking planner.
Enter your tank dimensions to see the volume.
The formulas
- Rectangular / square: length × width × height ÷ 1000 = litres (in cm).
- Cube: side³ ÷ 1000 = litres.
- Cylinder: π × (diameter ÷ 2)² × height ÷ 1000 = litres.
- Bow-front: the calculator approximates the curved front as an added parabolic segment — treat it as an estimate.
1 US gallon = 3.785 litres = 0.833 imperial gallons. Always measure the inside of the tank.
Common questions
How do I calculate aquarium volume?
Multiply length × width × height (in the same unit) to get the internal volume, then convert: 1 US gallon = 3.785 litres. For cylinders use π × radius² × height. The calculator above does this for rectangular, cube, cylinder and bow-front tanks.
Why is my real water volume lower than the calculated number?
Substrate, rocks, decorations and equipment displace water, and you never fill to the very top. Actual water volume is typically 10–15% below the geometric figure — plan stocking on the lower number.
Gallons or litres — which should I use?
Either; the calculator shows both, plus imperial gallons. Aquarium stocking advice is often given in US gallons, so the planner uses those.