Aquarium Volume Calculator
Instantly calculate the water capacity of your fish tank in litres. Accurately factors in glass thickness and recommended fill levels for precise results.
Rectangular or Cylindrical?
Select the shape of your aquarium to get an accurate volume calculation. Measuring in centimetres ensures the most precise litre conversion.
Rectangular Volume
Enter external dimensions and glass thickness for accuracy
Subtracts from internal volume
Leave space at the top (default 90%)
Rectangular Tank Result
Water capacity and weight estimation
Enter your tank dimensions, then click Calculate Volume.
Cylindrical Volume
Calculate capacity for round or column tanks
Measure straight across the middle
Subtracts from internal volume
Leave space at the top (default 90%)
Cylindrical Tank Result
Water capacity and weight estimation
Enter your tank dimensions, then click Calculate Volume.
Common Aquarium Sizes
Standard external dimensions and their approximate water volumes. Actual volume will vary slightly based on glass thickness and substrate.
| Tank Name | External Dimensions (L×W×H cm) | Approx. Volume (Litres) | Water Weight (kg) |
|---|---|---|---|
| Nano Cube | 30 × 30 × 35 | ~28 L | ~28 kg |
| 20-Gallon Long | 76 × 30 × 30 | ~68 L | ~68 kg |
| Standard 40 | 100 × 30 × 40 | ~110 L | ~110 kg |
| Standard 55 | 122 × 30 × 46 | ~160 L | ~160 kg |
| Standard 75 | 122 × 38 × 53 | ~220 L | ~220 kg |
| Standard 120 | 183 × 46 × 61 | ~450 L | ~450 kg |
Aquarium Volume FAQ
Everything you need to know about measuring and filling your fish tank.
To calculate the volume of a rectangular aquarium in litres, measure the internal length, width, and height in centimetres. Multiply these three numbers together (L × W × H) and then divide by 1,000. For example, a tank that is 100cm × 50cm × 40cm has a volume of 200,000 cubic cm, which equals 200 litres.
Yes, significantly for smaller tanks. Aquarium glass can be 4mm to 19mm thick. If you measure the outside of the tank, you must subtract the glass thickness from the length and width (twice, for both sides) and from the height (once, for the bottom) to get the true internal water volume.
No. It is recommended to leave about 2.5 to 5 cm (1-2 inches) of space at the top. This prevents water from splashing out, allows for surface agitation from filters, and accommodates the thickness of the lid or lighting fixtures.
Freshwater weighs approximately 1 kilogram per litre. Therefore, a 100-litre aquarium contains about 100 kg (220 lbs) of water alone. Saltwater is slightly heavier, weighing about 1.025 kg per litre. Always ensure your aquarium stand can support the total weight of the tank, water, substrate, and decorations.