The warmouth is somewhat larger than either rock bass or green sunfish (with which it is often confused) but very similar otherwise in that it is large-mouthed and heavy-bodied. Adult warmouth are dark, with mottled brown coloration. Their belly is generally golden, and males have a bright orange spot at the base of the dorsal fin. Three to five reddish-brown streaks radiate from the eyes, and the gill flaps are often red. Warmouth have three spines in the anal fin, 10 spines in the dorsal fin, and small teeth are present on the tongue. These fish range in size from 4 to10 inches (10.2 to 25 cm), but can grow to more than 12 inches (31 cm), and weigh up to 2.25 pounds (1 kg).