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Fish Tank Volume Calculator

Fish Tank Volume Calculator UK

Volume

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Enter your tank dimensions to see the volume.

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A fish tank volume calculator for the UK, showing results in litres and UK (imperial) gallons. Enter your dimensions and read the capacity instantly.

UK gallons and litres

In the UK, aquariums are usually measured in litres, but tanks are sometimes still listed in imperial gallons. One UK gallon equals 4.546 litres, which is larger than a US gallon.

Volume at a glance

Drag to fill a 60 by 30 by 30 cm (54 L) tank and watch the volume change.

50% full = 27 L

How to calculate fish tank volume

Measure the length, width and height of your tank, then multiply them together. Change the values below and the diagram and the calculation update instantly.

  1. 1

    Measure length, width and height

    60 x 30 x 30 cm

  2. 2

    Multiply them for cubic centimetres

    60 x 30 x 30 = 54,000 cm³

  3. 3

    Convert to litres and gallons

    54,000 ÷ 1000 = 54 litres (14.27 US gal)

Formulas behind the fish tank volume calculator

Prefer to calculate the aquarium size by hand? Here is the volume formula for each tank shape. Click a card to try it in the calculator.

For unusual tanks, see a triangular prism volume tool, and note that spherical aquariums (fish bowls) are not recommended for keeping fish.

Aquarium shapes

Our fish tank volume calculator supports seven popular aquarium shapes. Click any shape to load it into the calculator above.

Frequently asked questions

How do I calculate fish tank volume in the UK?
Measure in centimetres, multiply length by width by height, and divide by 1000 for litres. The result also shows UK gallons.
What is a UK gallon in litres?
One UK (imperial) gallon equals 4.546 litres, compared with 3.785 litres for a US gallon.
How many UK gallons is a 100 litre tank?
About 22 UK gallons (100 divided by 4.546).
Why does the UK use litres for tanks?
The UK uses the metric system for most measurements, so aquarium volumes are normally quoted in litres.
What units can I use in this calculator?
You can switch between centimetres, millimetres, inches, feet and metres at any time. Enter all dimensions in the same unit and the result updates instantly.
Does the result include substrate and decoration?
The figure is the full internal capacity. Subtract roughly 10 to 15 percent for substrate, rocks and the gap you leave at the top to estimate the real water volume.
How accurate is this fish tank calculator?
It uses the exact geometric formula for each shape, so the result is accurate for the dimensions you enter. Measure the inside of the tank for the best accuracy.
Is this calculator free to use?
Yes. It is completely free, needs no sign-up, and works on phones, tablets and desktops.

Calculator tools

Explore our specialised fish tank volume calculators, each tailored for a specific unit, shape or region.

In Gallons In Litres Tank Size Capacity Dimensions Water Volume Tank Weight In CM In MM In Inches In Feet Metric Hexagon Corner Cylinder & Round Bow-front Triangle Octagon Pentagon Surface Area UK Australia

Related guides

Learn the core ideas behind fish tank volume before or after using the calculator.