A cube aquarium has three equal edges, so a single measurement is enough. Cubes are popular for desktop and nano tanks, and the volume is simply the edge length cubed.
Small differences in edge length change the volume quickly: a cube with 40 cm edges holds 64 litres, while one with 42 cm edges holds about 74 litres. Measure carefully.
How is the volume of a cube aquarium calculated?
Gross volume (litres) = edge³ ÷ 1000 with the edge in centimetres, or edge³ ÷ 231 in inches for US gallons. For the net water volume, the glass thickness is subtracted in every direction, and the substrate and headroom are subtracted from the height.
How to take the measurements
- Measure one edge on the outside.
- Check the other two edges. If they differ, use the rectangular aquarium calculator instead.
- Measure the glass thickness at an edge.
- Enter the substrate height and headroom in the advanced settings.
Worked example
For a cube aquarium with edge length 40 cm, the gross volume is 64 litres. With 0.8 cm glass, no substrate and 2 cm of headroom, the net water volume is 54.9 litres.
Example sizes and their volumes
| Edge length (cm) | Gross (L) | Net water (L) | Net water (US gal) |
|---|---|---|---|
| 20 | 8 | 5.8 | 1.5 |
| 25 | 15.6 | 12.2 | 3.2 |
| 30 | 27 | 21.9 | 5.8 |
| 40 | 64 | 54.9 | 14.5 |
| 50 | 125 | 110.6 | 29.2 |
Net water volume assumes 0.8 cm glass, 0 cm substrate and 2 cm headroom; results are approximate.
Frequently asked questions
How many litres is a 30 cm cube aquarium?
30 × 30 × 30 = 27,000 cm³, which is 27 litres gross.
How many gallons is a 12 inch cube tank?
12 × 12 × 12 = 1,728 in³. Divided by 231 that is about 7.5 US gallons gross.
What if the edges are not exactly equal?
The cube formula is only exact for equal edges. For different edge lengths use the rectangular aquarium calculator.