how big do mice get
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).