Fish Tank Calculator
Calculate aquarium water volume in liters and gallons from tank dimensions, with a safe stocking estimate based on surface area.
About this tool
Enter your aquarium dimensions and get the true water volume in liters and gallons, plus a sensible stocking estimate for small fish.
Overstocking is the classic newbie collapse: fish growth and ammonia remain hidden until water quality fails. Knowing your actual volume is the base number for filtration, dosing and safe fish counts.
FAQ
How is aquarium volume calculated?
Length x width x height in cm, divided by 1000, gives liters. Subtract 10% for gravel and decor.
What is the 1-cm rule?
A common starter guideline is 1 cm of adult fish per liter of water, halved for messy species or a new tank.
Why does surface area matter?
Gas exchange happens at the surface: wide shallow tanks support more fish than tall narrow ones at the same volume.