This tool calculates the total internal volume of the tank. To find the exact "net" water capacity, you must subtract the volume taken up by substrate (gravel/sand), rocks, driftwood, and the empty space left at the top of the tank. A good rule of thumb is to subtract 10% to 15% from the gross volume.

Knowing your exact aquarium volume is critical for properly dosing water conditioners and medications, selecting appropriately sized filters and heaters, and determining how many fish you can safely stock without overloading the bioload.