Aquarium Volume Calculator

How to Calculate Aquarium Volume

Aquarium volume depends on tank shape. A standard rectangular tank uses length times width times height. Cylindrical tanks use $\pi r^2 h$. Bow-front tanks add a curved segment volume on top of the rectangular base.

Volume Formulas by Shape

Rectangular: $V = l \times w \times h$
Cube: $V = l^3$
Cylinder: $V = \pi (d/2)^2 h$
Half cylinder: $V = \pi (d/2)^2 h / 2$
Quarter cylinder: $V = \pi r^2 h / 4$

Frequently Asked Questions

How many gallons is a 20 gallon aquarium?

A standard 20 gallon tank holds about 20 US gallons when filled. Actual water volume is slightly less due to substrate, decorations, and the water line below the rim.

Does tank shape affect volume?

Yes. Bow-front and cylindrical tanks have different volume formulas than rectangular tanks of similar outer dimensions. Always use the correct shape formula.

How do I convert gallons to liters?

Multiply US gallons by 3.785 to get liters. This calculator shows both units automatically from your dimensions.

Should I fill the tank completely?

No. Leave space below the rim for equipment and to prevent overflow. Subtract substrate and decor volume for accurate fish stocking calculations.

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How to Calculate Aquarium Volume

Volume Formulas by Shape

Frequently Asked Questions

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