Aquarium Volume Calculator
Find how many litres or gallons a fish tank holds and how much the water weighs.
About the Aquarium Volume Calculator
Choose the tank shape and enter its inside dimensions (water height, not glass height). The calculator gives the water volume in litres and US and UK gallons, and the weight the stand must carry.
Volume is length × width × water height (not the tank's full height). 1 litre of fresh water weighs about 1 kg; seawater about 1.025 kg. Decorations and substrate displace some water, so dose medicines on the actual water volume, typically 80–90% of the glass volume.
The formula
Litres = L × W × H (cm) ÷ 1000
Worked example
A 48 × 13 × 18 inch tank
- 48 × 13 × 18 = 11,232 in³
- = 184.1 L (48.6 US gal)
- Water alone weighs about 184 kg (406 lb)
Questions people ask
How many fish can I keep?
Depends on species and filtration; avoid the old '1 inch per gallon' rule for large fish.
Can my floor take it?
Large tanks (300 L+) weigh hundreds of kg; place them over joists or on ground floors.