Aquarium Volume Calculator
Find how much water your aquarium holds. Enter the inside length, width and height in inches, then set a fill level to see the brimful and actual water volume in gallons and liters.
How to calculate aquarium volume
- Measure the inside length, width and height of the tank in inches.
- Enter the three dimensions.
- Set the fill level, usually about 90 percent below the rim.
- Read the brimful and actual water volume in gallons and liters.
Examples
24 by 12 by 16 in tank
24 in long, 12 in wide, 16 in tall, 90% fill
About 19.95 gallons full, 17.95 gallons of water (75.5 liters)
Frequently asked questions
How do I calculate aquarium gallons?
Multiply length by width by height in inches to get cubic inches, then divide by 231, since a US gallon is exactly 231 cubic inches.
Why use inside dimensions?
Glass and trim take up space. Measuring the inside of the tank gives the true water volume, which matters for stocking and dosing.
What fill level should I use?
Water usually sits below the rim, so about 90 percent is typical. Substrate, rock and decor displace water too, lowering the real volume further.
How do I convert gallons to liters?
Multiply gallons by 3.785412. The tool shows both so you can match food, medication and fertilizer doses given in either unit.
Does this work for a sump or refugium?
Yes, for any rectangular box. Enter its inside dimensions and a fill level to estimate the water it holds during operation.
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