Aquarium Calculator
Figure out exactly how much water your aquarium holds. Choose your tank shape, enter the dimensions, and get the volume in gallons and liters along with total water weight. Knowing your actual water volume is essential for dosing medications, fertilizers, and salt mixes.
Volume formulas by tank shape:
- Rectangular: Length x Width x Height
- Bow-front: Rectangular volume + the curved bow section (approximated as a half-ellipse)
- Cylindrical: pi x radius^2 x Height
Useful conversions:
- 1 cubic inch = 0.004329 US gallons
- 1 US gallon = 3.785 liters
- 1 gallon of freshwater weighs about 8.34 lbs (3.78 kg)
- 1 gallon of saltwater weighs about 8.56 lbs (3.88 kg)
Why fill level matters: Most aquariums are only filled to 90-95% capacity. Substrate, decorations, and equipment displace water too, so your actual water volume is usually 10-15% less than the full tank volume. Keep this in mind when dosing chemicals.