Aquarium Volume Calculator
Know exactly how much water your tank holds — essential for dosing, stocking, and equipment sizing.
Why Accurate Volume Matters
Knowing your exact water volume is critical for fish health. Medication dosing, fertilizer application, salt treatments, and water conditioner amounts all depend on precise volume measurements.
Substrate Displacement
A 2-inch layer of gravel in a 55-gallon tank displaces roughly 5-7 gallons of water. Our calculator subtracts substrate depth to give you the actual water volume, not just the tank's theoretical capacity.
Weight Considerations
Water is heavy — 8.34 lbs per gallon. Before setting up a large tank, verify that your floor can support the weight. A filled 75-gallon tank weighs over 700 lbs. Place large tanks on ground-floor rooms or structurally reinforced areas.
Volume Formula
231 cubic inches equals exactly 1 US gallon. For liters, multiply gallons by 3.785.