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Aquarium Volume Calculator

Find your aquarium’s volume.

Result

200.0 L
52.8 gal

How it is calculated

Enter the tank's length, width and height in centimetres. The tool treats the tank as a box: litres = length × width × height / 1000, because 1,000 cubic centimetres make one litre. US gallons are then litres × 0.264172. Results are rounded to one decimal place, and negative dimensions give no result.

This is the volume when the tank is filled to the very top using the dimensions you typed. Actual water volume is smaller because of glass thickness, the gap below the rim, gravel or sand, rocks and decorations. Use inside dimensions for a closer figure, and check the result against your tank's listed capacity before dosing medicine or salt.

Worked example

A tank is 100 cm long, 40 cm wide and 50 cm high. The volume is 100 × 40 × 50 = 200,000 cubic centimetres. Divide by 1,000 and you get 200.0 L. In US gallons that is 200 × 0.264172 = 52.8 gal. With substrate and a few centimetres of space below the rim, the real water volume will likely be noticeably lower.

Try this example →

Common mistakes

  • Entering dimensions in inches or millimetres; the formula expects centimetres.
  • Using the outside dimensions of the glass and treating the result as the water volume.
  • Measuring full height when the water level is 3 to 5 cm lower, which overstates the volume and the dose of medication.
  • Mixing US and imperial gallons; the gallon figure here is the US gallon (3.785 L).

About this calculator

This calculator finds an aquarium's water volume in liters and gallons from its length, width, and height, using the simple box formula volume = length × width × height, then converting to the units fishkeepers actually shop and dose by.

Aquarium hobbyists use it to size a new tank, calculate how much water a water change involves, and work out correct dosing for medications, fertilizers, or dechlorinator (most products are dosed per liter or per gallon). It also helps when choosing a filter or heater rated for a specific tank volume.

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Comments (1)

  • Editorial team

    Once you have the litres, remember that fresh water weighs about 1 kg per litre. A 200 L tank holds roughly 200 kg of water before glass, substrate and rock, which matters for the stand and the floor underneath, especially in an upper-floor flat. That load is worth checking before you buy the tank. If you have set up a tank with an odd shape, tell us how you worked out its volume.

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