Betta fish can grow to about 5 cm in natural state, and very few can grow to about 12 cm. Different regions, species and feeding methods will affect the body length of betta fish.

It can grow about 0.8-1cm from childhood to 1 month, and it only takes about half a year to adulthood. It will not grow when it grows to about 8cm, so the fish with a body length of 10cm or more are more than one year old, and the lifespan of the betta fish will come to an end after two years or so.