Planning a new fish tank? Enter your aquarium’s dimensions to calculate its water volume in litres and gallons, the weight of the water, a recommended heater size and how much substrate you will need — free, private, and with no sign-up.
Heater guidance follows the common 1 watt per litre rule of thumb; substrate assumes a 5 cm bed.
How to Use
- Choose your tank shape — rectangular or cylindrical — and the units you measured in.
- Enter the length (or diameter), width and height of the tank.
- Read the live results: volume in litres and US gallons, water weight, heater size and substrate.
Key Features
- Rectangular and cylindrical tanks — the inputs adapt to the shape you choose.
- Metric and imperial — enter dimensions in centimetres or inches.
- More than just volume — water weight, heater wattage and substrate estimates included.
- Live calculations — every result updates the moment you change a value.
- 100% private — everything is calculated in your browser and never sent to a server.
FAQs
Is this aquarium calculator free to use?
Yes. The calculator is completely free with no sign-up, no usage limits and no hidden charges.
What heater size does my tank need?
A common rule of thumb is about 1 watt of heater power per litre of water for a tropical tank in a normally heated room. The calculator applies this rule; use it as a starting guide and check with your aquarium shop for unusual setups.
How much substrate do I need?
The estimate assumes a 5 cm deep bed of gravel or sand across the base of the tank, which suits most freshwater setups. Planted tanks sometimes need a deeper bed.
Is my data uploaded or stored anywhere?
No. All calculations happen locally in your browser using JavaScript, so your inputs never leave your device.
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