Quick answer: Size of droppings, gnawing, tracks, noises, nesting evidence and sighting size can help distinguish rats from mice. When the evidence is unclear, inspection is more reliable than guessing.
Droppings can provide a clue
Rat and mouse droppings differ in size, but appearance alone is not always enough. Consider the location, quantity and other evidence around them.
Look at the scale of gnawing and damage
Larger damage and openings may suggest rats, while smaller signs can point toward mice. Building conditions and access routes also matter.
Listen to where activity occurs
Both rats and mice can move through hidden spaces. Note whether sounds are concentrated in walls, ceilings, cabinets, basements or other areas.
Why correct identification matters
Control and exclusion decisions should fit the actual rodent. A rodent-control inspection can help identify the problem before a plan is selected.