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About Aquarium Volume Calculator

Whether you are keeping a simple Goldfish bowl or a massive Reef Tank, knowing the exact volume of water is the single most important variable in fishkeeping.

Why Accuracy Matters

  • Dosing Medication: Fish meds are potent. Dosing for 50 gallons in a 40-gallon tank can kill your livestock. Dosing too little effectively creates drug-resistant bacteria.
  • Heater Sizing: You generally need 3-5 watts of heating power per gallon.
  • Stocking Limits: The biological filter can only handle a certain bio-load per liter of water.

The Math

Calculating volume from dimensions is simple geometry:
Volume = Length * Width * Height
However, conversion is tricky.
1 Cubic Inch = 0.004329 Gallons.
1 Cubic Centimeter = 0.001 Liters.

Displacement Warning

Remember that rocks, sand (substrate), and decorations displace water. A "55 Gallon" tank full of rocks might only hold 45 gallons of actual water. Always under-estimate volume when stocking, and be precise when dosing.