Aquarium volume calculator
Litres and US gallons from tank dimensions — then see what actually fits in it.
Volume
180 litres
≈ 47.6 US gallons
Substrate, hardscape and the waterline typically leave 85–90% of that as actual water — the stocking planner models this through your aquascape settings instead of guessing.
Check what fish fit in this tankThe number printed on the box is the volume of an empty glass rectangle, and you are never going to have one of those. Start from outside dimensions and you are already over: 6 mm glass on a 60 cm tank costs more than a litre before anything goes in. Then the water stops a few centimetres below the rim, because a full-to-the-brim tank splashes and leaves no room for a lid or a spray bar — call it 5 cm of freeboard. Then substrate: a 5 cm bed across a 60 × 30 cm footprint displaces around nine litres, and every rock and piece of wood takes its own share. Add it up and a tank sold as 60 litres holds nearer 45 once it is running, which is a quarter of the volume you thought you had. That matters twice over. Dose a fertiliser or a medication on the box figure and you are overdosing by a quarter — for medication that is the difference between treatment and poisoning. Stock on the box figure and every capacity calculation downstream inherits the error. So this tool gives you the glass volume, and then tells you what to subtract, because the honest number is the one your fish actually swim in.
Common questions
- How do I calculate aquarium volume in litres?
- Multiply length × width × height in centimetres and divide by 1,000. A 100 × 40 × 45 cm tank works out to 180 litres — before substrate, hardscape and the gap above the waterline take their share.
- How many litres is a US gallon?
- One US gallon is 3.785 litres. UK (imperial) gallons are larger at 4.546 litres, which is why "gallon" advice from different sources can quietly disagree.
- How much volume does substrate take?
- Roughly the footprint times the depth, minus the water that stays in the gaps between grains — in practice about two thirds of the raw displacement for gravel, closer to three quarters for fine sand. A 5 cm bed over 60 × 30 cm works out near 6–9 litres. If you are dosing medication, measure rather than estimate: fill a jug, pour it in, and count.