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Fish Tank Volume Calculator

Fish Tank Surface Area Calculator

Surface area

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Enter your tank dimensions to see the volume.

Did we solve your problem?

Work out the water surface area of your aquarium, which affects oxygen exchange. Enter the dimensions to see the surface area and the full volume.

Why surface area matters

The water surface is where oxygen enters and carbon dioxide leaves, so it is length times width for a rectangular tank. A wide, shallow tank holds more oxygen than a tall, narrow one of the same volume.

Water surface area

length width

The water surface is length times width. Adjust the sides to see the area.

Surface area = 1,800 cm²

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 surface area?
For a rectangular tank, multiply length by width. That is the top opening where gas exchange happens.
Why is surface area important for fish?
A larger surface lets more oxygen dissolve, which supports more fish and healthier water.
Is a tall tank worse for oxygen?
A tall, narrow tank has less surface for its volume, so it holds less oxygen than a wide tank of the same size.
How does surface area relate to stocking?
Some aquarists stock by surface area rather than volume, allowing roughly a set length of fish per area of surface.
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.