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Fish Tank Volume Calculator

Fish Tank Capacity Calculator

Volume

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Enter your tank dimensions to see the volume.

Did we solve your problem?

Find out how much water your aquarium can hold. Enter the dimensions and the capacity is shown in litres, US gallons and UK gallons.

What is fish tank capacity?

Capacity is the full internal volume of the tank. The real water it holds is a little lower, because substrate, rocks and the fill gap take up space, usually 10 to 15 percent.

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 capacity?
Multiply length by width by height, then convert to litres or gallons. Subtract 10 to 15 percent for substrate and the top gap to estimate usable water.
Is capacity the same as volume?
Yes, the full capacity equals the calculated volume. The actual water volume is slightly lower once the tank is set up.
Why is my tank's real capacity lower?
Substrate, rocks, decor and the gap you leave at the top all reduce the water the tank actually holds.
How do I find capacity in gallons?
Switch the result unit to US or UK gallons, or calculate litres and multiply by 0.264 for US gallons.
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.