About Fish Tank Volume Calculator

Fish Tank Volume Calculator is a free, fast and accurate tool for working out the water volume and capacity of any aquarium. Whether you keep a nano shrimp tank or a large reef system, knowing your exact volume is the foundation of healthy fishkeeping.

Why we built it

Dosing medications, adding water conditioner, choosing a heater wattage and stocking your tank all depend on one number: how much water your tank actually holds. We built this calculator so you never have to guess — just enter your dimensions and get instant results in litres and gallons.

How it works

Our calculator supports rectangular, cube, cylinder, hexagon, corner and bow-front tanks. It converts your measurements from any common unit and returns the volume in litres, US gallons, UK gallons and cubic centimetres.

Accuracy

Results reflect the full internal capacity of the tank. Remember that substrate, rocks, décor and the gap you leave at the top reduce the actual water volume — usually by 10–15%.

Questions or feedback? Get in touch.