The maximum length of the common map turtle is about 11 inches. Males are much smaller than females, with a maximum length of about 5.5 inches. The shell is moderately low and flattened, with a central keel. The carapace is smooth, with a slightly serrated rear margin, and a reticulate pattern of light lines on an olive background. The head and legs are olive to dark brown with light stripes. There is nearly always a somewhat elongated spot behind the eye.