Lakeland, FL Homefacts Overview of Polk County includes data on offenders, schools, foreclosures, environmental hazards, and more.
Adult mice have bodies that are 3-4 inches long with 3-4 inch tails. Adult rats are far heavier and longer: they can weigh ten times as much, averaging 350-450 grams for females and 450-650 for males (with an overall range of 200-800 grams). They have 9-11 inch long bodies and 7-9 inch tails (ref).
Mice are more brown to begin with, and have darker bellies. Next is the tail. It's black with scaley rings on a rat, and tan and more smooth on a mouse. The feet of a rat are also longer in proportion to the body, and a rat's ears are also larger. But these variations are subtle. The primary thing, of course, is the size difference.