Aquarium Volume Calculator — Free Online Tool

How to use the Aquarium Volume Calculator

Estimate aquarium usable water volume in liters, US gallons and Imperial gallons for rectangular and cylindrical tanks using inside dimensions, water depth, substrate and decoration displacement.

1. Select a rectangular or cylindrical tank shape and inches or centimeters.
2. Measure inner—not exterior—tank dimensions and the actual water line.
3. Enter the approximate excluded substrate depth and hardscape displacement.
4. Use the resulting liters and gallons as an estimate rather than the marketed outer tank capacity.

Accuracy note: For approximate water capacity, not structural load rating, safe stocking limits or aquarium stand approval.

Aquarium Volume Calculator formula and method

Geometric volume = internal base area × effective water height. Effective height = actual water depth − excluded substrate depth. Estimate usable water by multiplying by (1 − decor displacement%).

All numeric results depend on entered measurements, dimensions and settings. Intermediate calculations retain decimal precision; displayed results may be rounded. Verify material specifications, relevant laws and seller fee conditions where applicable.

Worked example

An internal 12 × 12 × 12-inch rectangle contains 1,728 cubic inches = 28.32 liters before substrate or decoration displacement.

Adjust the values in the interactive tool above to reproduce this example or model your own situation.

Frequently asked questions