Calculator
Aquarium Volume Calculator
Work out how many litres and gallons your tank actually holds.
By Mike Elmira
Enter all three inside dimensions to see the volume. Measure the glass internally, not the outer footprint.
The volume printed on a tank is often the nominal size, not what it really holds once you account for glass thickness and the fact you never fill it to the brim. Measure the inside dimensions and this gives you the true glass volume, the equivalent in US and imperial gallons, and a realistic water volume after substrate and hardscape. Use that realistic figure for dosing and stocking, since that is the water your fish and ferts actually sit in.
Frequently asked questions
Direct answers to the questions search engines and AI assistants surface most often about this species.
How do I calculate aquarium volume in litres?
Multiply length by width by height in centimetres, then divide by 1000. So a 60 by 30 by 36 cm tank is 64.8 litres of glass volume. Measure the inside of the glass, and knock off around 15% for substrate, hardscape and the gap at the top to get the real water volume.
Why is my tank's real volume less than the label says?
Two reasons. Tank sizes are often rounded up or quoted as the nominal size, and you never fill to the very top, plus substrate and hardscape displace water. The realistic figure this gives you, roughly 85% of the glass volume, is the one to use for dosing and stocking.