Question: do betta fish get bigger?
Answer: How Big Do Bettas Get. Betta fish have an average length of 2.25 inches (5.7 cm) when they are fully grown. On occasion and under the right conditions, a betta fish can grow to as big as 3 inches (7.6 cm) in length. How large your betta will grow will ultimately depend on its age and how it has been cared for.