Enter the number of goldfish and the standard size per goldfish into the calculator to determine the tank size. This calculator can also evaluate any of the variables given the others are known.

Goldfish Tank Size Formula

The following formula is used to calculate the appropriate size for a goldfish tank.

TS = G * S


  • TS is the tank size in gallons G is the number of goldfish S is the standard size per goldfish in gallons (usually 20 gallons for the first goldfish and 10 gallons for each additional one)

To calculate the appropriate tank size for goldfish, multiply the number of goldfish by the standard size per goldfish. This will give you the total tank size in gallons.

What is a Goldfish Tank Size?

A goldfish tank size refers to the capacity of the aquarium where goldfish are kept. The size of the tank is crucial for the health and well-being of the goldfish as they require ample space to swim and grow. The recommended minimum size for a goldfish tank is 20 gallons for the first fish and an additional 10 gallons for each additional fish. This allows for proper filtration, reduces the concentration of waste, and provides enough oxygen for the fish.

How to Calculate Goldfish Tank Size?

The following steps outline how to calculate the Goldfish Tank Size.

  1. First, determine the number of goldfish (G).
  2. Next, determine the standard size per goldfish (S) in gallons.
  3. Next, gather the formula from above = TS = G * S.
  4. Finally, calculate the Goldfish Tank Size (TS).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

number of goldfish (G) = 3

standard size per goldfish (S) = 20 gallons