Mice are smaller; rats are larger
Mice have smaller, more delicate bodies; rats have thicker, sturdier bodies
Mice have proportionally larger ears and eyes; rats have smaller ears and eyes relative to their heads
Mice have thinner, more pointed snouts; rats have blunter, broader snouts
Mice have long, thin tails about the same length as their bodies; rats have thicker tails that are often shorter than their bodies
Mouse droppings are small and pointed; rat droppings are larger and more capsule-shaped
Mouse tracks are smaller and finer; rat tracks are larger and heavier
Mouse sounds are usually lighter scratching or squeaking; rat sounds are often louder and heavier
Mice tend to leave smaller gnaw marks; rats leave larger gnaw marks
Mice usually fit through very small openings; rats need larger gaps