Pet
Aquarium Water Volume Calculator
Calculate aquarium volume in litres and gallons from length, width and height.
The result gives the gross volume in litres and US gallons, plus a lower usable volume, so the usable figure is the amount of water actually available after substrate and decor take up space.
Formula
Volume in litres equals length times width times height in centimetres, divided by 1000.
How it works
Internal dimensions multiply to cubic centimetres, converted to litres. Substrate, rocks and equipment displace water, so usable volume is shown about 10% lower.
Worked example
For example, with a length of 100 cm, a width of 40 cm, and a height of 50 cm, the gross volume is 200 litres (52.8 US gallons), and the usable volume is roughly 180 litres.
FAQs
Should I measure inside or outside?
Inside, since glass thickness reduces real volume.
Why does usable volume matter?
Stocking, dosing and filtration all depend on real water, not glass size.
Are UK and US gallons different?
Yes. This page uses US gallons; UK gallons are larger.
General information only, not veterinary advice.
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