Aquarium Volume Calculator

Find an aquarium’s water volume in litres and gallons from its dimensions, with an allowance for substrate and freeboard. Calculates in your browser.

Water volume

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US gallons-
Imperial gallons-

Show the math

Volume is the tank's internal dimensions multiplied together, then converted to litres and gallons:

litres = length × width × height (cm) ÷ 1000

A cylinder uses π × r² × height. The "filled to" percentage accounts for substrate, rocks and the gap left below the rim, actual water is usually 85–90% of the gross capacity.

1 US gallon = 3.785 L · 1 imperial gallon = 4.546 L. Everything is calculated in your browser.

What this does

An aquarium volume calculator finds a tank’s water volume in litres and gallons from its dimensions, with an allowance for substrate and freeboard.

How to use it

  1. Choose the tank shape.
  2. Enter the dimensions.
  3. Set the "filled to" percentage.
  4. Read litres and gallons.

How it works

Cylinders use π × r² × height. Substrate, rocks, and the gap below the rim mean real water volume is usually 85–90% of the gross size.

litres = L × W × H (cm) ÷ 1000

Understanding your result

The real water volume is usually only 85 to 90 percent of the gross size once substrate, rocks, and the gap below the rim are counted, so use the adjusted figure when dosing treatments or choosing stock levels. Overstocking and overdosing both trace back to an overestimated volume.

Example

A 60 × 30 × 36 cm tank holds about 65 litres.

Sources & methodology

Last updated .

Frequently asked questions

How do I work out tank volume?

Multiply length × width × height (in cm) and divide by 1000 for litres; cylinders use π × r² × height. The tool also converts to US and imperial gallons.

Why is actual water less than the size?

Substrate, rocks and the gap below the rim mean the real water volume is usually 85–90% of the gross capacity, which the "filled to" percentage accounts for.

Is anything stored?

No. Everything is calculated locally in your browser.