Aquarium Volume Calculator — Fish Tank Size in Litres
Find out how many litres your fish tank holds. Enter the tank dimensions, glass thickness and fill level to get the net water volume, total weight and a visual of your aquarium.
Tank shape
cm
cm
cm
%
mm
Volume of water at the chosen fill level
170 L
water- 1
Gross tank volume
90 × 45 × 50 ÷ 1000 = 202.5 - 2
Net interior volume
88.4 × 43.4 × 49.2 ÷ 1000 = 188.8Inner dimensions after subtracting glass panel thickness on each face. - 3
Water volume
188.8 × 90% = 169.9
How does this calculator work?
Rectangular: V (L) = L × W × H / 1000. Cylindrical: V = π × r² × H / 1000. Subtract glass volume and fill to ~90% for actual water volume. Freshwater weighs 1 kg/L; saltwater ~1.025 kg/L. Always account for total structural weight when siting a large tank.
Formula
How this is calculated
For a rectangular aquarium the gross volume is simply length × width × height (all in centimetres) divided by 1,000 to convert cubic centimetres to litres. The calculator then subtracts the glass displacement — the volume occupied by the 5 panels (front, back, two sides and base) — to give the net interior volume. Dividing the net volume by a fill-percentage factor (typically 90%) yields the actual water volume, since aquarists leave head-space at the top for filters, skimmers and oxygen exchange.
For a cylindrical tank the gross volume is π × r² × H / 1000, where r is the internal radius and H is the height. The same fill adjustment applies.
Water weighs almost exactly 1 kg per litre for freshwater at room temperature. Saltwater (typical reef density ≈ 1.025 g/mL) weighs about 2.5% more. Combined with the weight of the glass, substrate, rock and equipment, this total gives you the structural load the stand and floor must support — important for large tanks over 200 L. Always add the dry weight of glass, rocks and decor when assessing floor loading.
Frequently asked questions
The glass panels occupy space inside the nominal footprint. For example, an 8 mm glass aquarium with a 90 × 45 × 50 cm outer dimension has an inner volume about 5–8 litres smaller than the gross figure. The fill level (typically 88–95%) further reduces the usable water volume because aquarists leave head-space for equipment and evaporation.
1 US gallon = 3.785 litres; 1 UK/Imperial gallon = 4.546 litres. So a 200-litre tank is about 52.8 US gallons or 44.0 UK gallons. Fish stock recommendations on many English-language sites use US gallons.
Volume is a key factor but not the only one. Filtration capacity, surface area for gas exchange, the specific needs of the species and regular water change frequency all matter. A common starting guide is 1 cm of adult fish length per 1–2 litres of water, but this is a very rough rule. Research each species' specific requirements.
Also known as
TG we-Calculate Editorial Team. (2026). Aquarium Volume Calculator — Fish Tank Size in Litres [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/aquarium-volume-calculator
TG we-Calculate Editorial Team. "Aquarium Volume Calculator — Fish Tank Size in Litres." TG we-Calculate. 2026. https://we-calculate.com/calculator/aquarium-volume-calculator.
TG we-Calculate Editorial Team, "Aquarium Volume Calculator — Fish Tank Size in Litres," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/aquarium-volume-calculator
@misc{wecalculate_aquarium_volume_calculator, title = {Aquarium Volume Calculator — Fish Tank Size in Litres}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/aquarium-volume-calculator}}, year = {2026}, note = {TG we-Calculate} }
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