How big are terrapin turtles?

Terrapin turtles typically range in size from about 4 to 10 inches in carapace length, depending on the species. The most common species, the Eastern Box turtle, averages around 5 to 7 inches. In contrast, larger species like the Diamondback terrapin can reach up to 9 inches or more. Generally, they are considered small to medium-sized turtles.