Tank Volume Calculator
Enter the inside dimensions of a rectangular tank, aquarium or cylinder to find its capacity in US gallons and liters and the weight of water it holds.
Result
- Imperial gallons
- 43.6 UK gal
- Cubic feet
- 7 cu ft
- Cubic inches
- 12,096 cu in
- Weight of fresh water
- 436.1 lb
Water weight uses fresh water at room temperature, 0.998 kg per liter. Use inside dimensions for true capacity.
Formula
- Rectangular: volume = length × width × height
- Cylinder: volume = π × (diameter ÷ 2)² × length
- 1 US gallon = 231 cubic inches = 3.78541 liters
How the Tank Volume Calculator works
Tank capacity is its inside volume. For a box that is length times width times height. For a cylinder, standing or lying down, it is the area of the circular end times the length.
Aquariums are sold by nominal gallons based on outside dimensions, so the true water volume is a little lower once glass thickness, substrate and the gap at the top are taken out.
Worked example
A tank 48 in × 12 in × 21 in has a volume of 12,096 cubic inches. Dividing by 231 gives 52.36 US gallons, or 198.2 liters. The water weighs about 436 lb.
Frequently asked questions
How do I calculate gallons from inches?
Multiply length, width and height in inches and divide by 231, the number of cubic inches in a US gallon.
How much does a gallon of water weigh?
A US gallon of fresh water weighs about 8.34 pounds at room temperature. A 55 gallon aquarium holds roughly 459 pounds of water.
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