The Bullfrog is a large frog attaining lengths in excess of 6 inches. The dorsal color is usually a dull green, but may be brownish.
Some specimens are dark gray to black.
There are usually no markings on the dorsal surface. The ventral surface is often ranges between shades of white to yellow. They have little to no dorsolateral ridges . Like many species of Rana , the tympanic membrane is helpful in determining the gender of the individual. In females, the membrane will be roughly equal to the size of the eye and in males the membrane will be considerably larger.