How to Calculate Round Aquarium Volume

Written by chris smith
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How to Calculate Round Aquarium Volume
Goldfish are traditionally kept in round tanks known as goldfish bowls. (Viewstock/Photodisc/Getty Images)

Choosing the right size fish tank is important because some fish and aquatic plants often require a specific amount of space in which to thrive. Larger or more active aquatic animals will require more swimming space. Round tanks can take up less space while holding the same amount of water as rectangular tanks. The volume of a round or spherical fish tank can be determined by taking one measurement and using three equations.

Skill level:

Things you need

  • Measuring tape marked in centimetres
  • Calculator

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  1. 1

    Measure the circumference of the spherical fish tank using a measuring tape marked in centimetres (cm). The circumference is measured around the equator of the aquarium, which is its widest part. For example, the circumference could be 100cm.

  2. 2

    Determine the radius of the fish tank by using this equation: radius = C/2pi, where C is the circumference that was measured in centimetres and pi is approximately equal to 3.14. In the example, 100/(2 x 3.14) = 15.9. The radius of your tank is 15.9cm.

  3. 3

    Calculate the volume of the spherical aquarium with this equation: volume = (4/3)pi(radius^3). In the example, 4/3 x 3.14 x 15.9^3 = 16829. The volume of your tank is 16,829 cubic centimetres.

  4. 4

    Divide your tank volume in cubic centimetres by 1000. In the example, 16829/1000 = 16.829. The liquid volume of your tank is about 17 litres.

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