What size openings can mice squeeze through?

• A. 1/2 inch
• B. 1/4 inch
• C. 3/8 inch
• D. 1 inch

Answer: (B)

Mice can get through surprisingly small openings because their bodies are compact and very flexible. The smallest opening they can squeeze through is about 1/4 inch in diameter, roughly the thickness of a pencil. That’s the threshold at which entry becomes possible; openings smaller than that are generally too tight for a mouse to pass. So the best answer reflects this minimum entry size. In practical pest-proofing, seal gaps no larger than 1/4 inch to prevent mice from getting inside. Larger gaps, such as those around 1/2 inch, 3/8 inch, or 1 inch, are all capable of allowing entry, but they illustrate openings bigger than the minimum that mice can already exploit.