Aquarium Volume Calculator
Estimate usable rectangular aquarium water volume.
Estimate aquarium volume
Use inside dimensions for a rectangular aquarium.
Volume estimate
US gallons
About 15.71 US gallons, or 59.47 litres, of water.
- Liters
- 59.47 L
- Adjusted water height
- 12.6 in
- Rectangular water space
- 3,628.8 cu in
Decorations, equipment, and irregular shapes reduce actual water volume.
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Estimate aquarium water volume
Measure the aquarium’s inside length, width, and height in inches. Enter average substrate depth and the percentage of the remaining height you expect to fill.
The result is a rectangular geometric estimate in US liquid gallons and liters. Actual water volume is normally lower because rocks, wood, decorations, filters, equipment, uneven substrate, and curved or irregular walls displace water.
Formula
Water height equals inside height minus substrate depth, multiplied by fill percentage. Cubic inches equal inside length multiplied by inside width and adjusted water height.
US gallons equal cubic inches divided by 231. Liters equal cubic inches multiplied by 0.016387064.
Using the estimate
Use measured water additions for more precise dosing or maintenance records. This tool does not determine appropriate stocking, filtration, heating, medication, structural support, or animal care. Verify equipment specifications and seek knowledgeable guidance for the species and system.
Frequently asked questions
Why should I enter inside dimensions?
Outside dimensions include the tank walls and therefore overstate the interior space. Inside dimensions give a closer geometric estimate.
How are substrate and fill level handled?
Substrate depth is subtracted from inside height. The remaining height is multiplied by the fill percentage before calculating rectangular volume. Substrate is treated as solid, so water held between grains is not counted and the real volume can be somewhat higher than this figure.
Will the aquarium hold exactly this much water?
Usually less. Decorations, equipment, uneven substrate, wall thickness, curved shapes, and space above the waterline displace or remove volume.
Can this determine safe stocking or equipment size?
No. Animal needs, tank shape, filtration, surface area, water quality, species compatibility, and husbandry matter. Use appropriate expert guidance rather than volume alone.