How long can a goldfish be?

Goldfish vary in size depending on the species and environment in which they live. In general, goldfish can range from about 2 to 12 inches in length. Common goldfish (Carassius auratus) typically grow to be about 6 to 8 inches long, while some larger varieties, such as the comet goldfish (Carassius auratus comet) can reach lengths of up to 12 inches or more.