How it works
Enter the outside dimensions of your fish tank (length, width/depth, and height). The calculator finds the gross volume of the empty tank. Since aquariums are never filled to the absolute brim, and space is taken up by glass thickness, substrate (gravel/sand), and decorations, we provide an "Actual Water Fill" percentage. By default, this is set to 90%, meaning the calculated water volume is 90% of the tank's maximum physical capacity.
Example
Scenario: You have a standard "60cm tank" (60x30x36 cm) and want to know how much water to prepare for the initial fill.
- Gross Capacity (Empty): 60 x 30 x 36 cm = 64.8 Liters.
- Deductions: You add a few inches of substrate and leave a 2cm gap at the top. You estimate the actual water volume will be about 85% of the gross capacity.
- Calculation: 64.8 Liters × 85% = ~55 Liters.
Verdict: You only need to treat and prepare about 55 Liters of water, not the full 64.8 Liters.
FAQ
Why do I need to know the exact water volume?
Knowing your true water volume (not just the gross tank size) is critical for properly dosing medications, adding water conditioners, and sizing your heater and filter.
What is the difference between US Gallons and Imperial Gallons?
A US Gallon is exactly 3.78541 liters, whereas a UK/Imperial Gallon is 4.54609 liters. This calculator provides both to avoid confusion depending on where you live.