Aquarium Volume Calculator
By Santaji GadepatilinUpdated October 27, 2026
An aquarium's water volume decides how many fish it can hold, the filter and heater size, and treatment doses. This free aquarium volume calculator solves for whichever value you leave blank and shows the formula and steps.
How to use the aquarium volume calculator
Enter the tank’s length, width and water height. The volume and weight of the water are calculated.
Example
A 100 × 40 cm tank filled to 45 cm: 100 × 40 × 45 = 180,000 cm³ = 180 litres (47.6 US gal), weighing about 180 kg of water.
Common tank sizes
| Tank (L × W × H) | Volume | Water weight |
|---|---|---|
| 40 × 25 × 25 cm | 25 L (7 US gal) | 25 kg |
| 60 × 30 × 35 cm | 63 L (17 US gal) | 63 kg |
| 80 × 35 × 40 cm | 112 L (30 US gal) | 112 kg |
| 100 × 40 × 50 cm | 200 L (53 US gal) | 200 kg |
| 120 × 45 × 50 cm | 270 L (71 US gal) | 270 kg |
| 150 × 50 × 60 cm | 450 L (119 US gal) | 450 kg |
Actual water volume
Substrate, rocks, decorations and the gap at the top reduce the real water volume by about 10–20%. Use the real volume when dosing medicines, fertilisers or water conditioners.
Total weight
A filled aquarium weighs roughly: water + glass + substrate + rock. As a rule of thumb, allow about 1.2–1.4 kg per litre of tank volume. A 200 L tank can weigh 250–280 kg, so make sure the stand and floor can support it.
Filtration and heating
| Equipment | Rule of thumb |
|---|---|
| Filter flow | 4–6 times the tank volume per hour |
| Heater | about 1 W per litre (more in cold rooms) |
| Water change | 10–25% weekly |
Stocking
The old “one inch of fish per gallon” rule is unreliable. Consider adult fish size, activity, waste output and the tank’s footprint. Larger tanks are more stable and forgiving for beginners.
Other shapes
- Cylinder: π × r² × height.
- Bow-front: approximate with a rectangle using the average depth.
Frequently asked questions
How do I calculate aquarium volume?
Multiply length × width × water height in cm and divide by 1,000 to get litres.
How heavy is a full aquarium?
Water alone weighs about 1 kg per litre; add the glass, gravel and decorations — roughly another 20–30%.
How many fish can I keep?
Old "1 inch per gallon" rules are unreliable. Consider adult fish size, behaviour and filtration, and ask a specialist.
How many litres is a 60 × 30 × 35 cm tank?
63 litres, or about 17 US gallons.
How much does a 100 litre aquarium weigh?
About 120–140 kg when filled, including glass and substrate.