Aquarium Volume Converter

Aquarium volume from dimensions.

Formula:

• Volume (gallons) = Length x Width x Height / 231 (all measurements in inches; 231 cubic inches = 1 US gallon)
• Volume (liters) = Length x Width x Height / 1000 (all measurements in centimeters)

Common standard tank sizes:

Weight of water:

• 1 US gallon of water = 8.34 lbs (3.78 kg)
• A full 55-gallon tank weighs about 460 lbs (209 kg) with water.

That water-weight line at the end is the one that actually matters before you buy. Water is heavy, about 8.3 pounds a gallon, and a tank concentrates it onto a small footprint. A 55-gallon setup with rock and substrate pushes past 600 pounds, which is more than most furniture is built for, so it needs a proper aquarium stand and, for anything over about 40 gallons, a floor that can take the point load. People who skip this learn it the expensive way.

There’s also a gap between the number you calculate and the water actually in the tank. Substrate, rocks, and decorations displace volume, and you never fill to the very brim, so real water volume usually runs 10 to 15% below the geometric figure. That matters whenever you dose medication or water conditioner, because those are measured per actual gallon: dose by the full calculated volume and you’ll overdose a tank that’s really holding less. For stocking and chemicals, estimate the net water volume, not the box’s nominal size.