Aquarium Volume Calculator

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. A 24 by 12 by 16 inch tank is 4,608 cubic inches, which is about 19.95 gallons.

US gallons, which are exactly 231 cubic inches each. An imperial (UK) gallon is larger at about 277.42 cubic inches, so the same tank would read a smaller number of imperial gallons. The liters figure is unit neutral.

Glass and trim take up space, so outside dimensions overstate the tank. Measuring the inside gives the true water volume, which is what matters for stocking, medication and fertilizer dosing.

Water usually sits below the rim, so about 90 percent is typical for a rimmed tank. Enter 100 percent for a brimful reef or rimless build, or lower if you keep a large air gap.

Yes. Sand, gravel, live rock and hardscape all displace water, so the water your tank actually holds is less than the calculated figure. Heavily aquascaped tanks can lose 10 to 20 percent or more, and this tool does not subtract that.

Multiply US gallons by 3.785412. The calculator shows both at once so you can match food, medication and fertilizer doses whether they are labeled in gallons or liters.

Yes, for any rectangular box. Enter its inside dimensions and the operating water level as the fill percent to estimate the water it holds while running.

No. This calculator assumes a rectangular box, so length times width times height. A curved bowfront reads slightly high, and cylinders or hex tanks need their own area formula rather than this one.

The math is exact; the display rounds gallons to two decimals, liters to one and cubic inches to a whole number. Everything runs in your browser, so nothing you type is uploaded.