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Betta Tank Size Calculator

Measure the tank you have or are considering, and get a straight answer: how many gallons it holds, and whether that is enough.

Last updated

This calculator does the arithmetic. The reasoning behind the numbers is in What Size Tank Does a Betta Fish Need? The Honest Answer, which this tool follows exactly: 5 US gallons is the practical minimum we recommend for one betta, not a bowl or a vase.

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Measure the inside of the tank at its widest points. The result is the tank's brim volume — substrate, decor and the waterline you actually keep will reduce the water it holds a little below this figure.

What are you planning to keep in this tank?