1. Same width, different thickness
The CR2032 is 3.2 mm thick and the CR2025 is 2.5 mm. Both are exactly 20 mm across, so a CR2025 will drop into a slot made for a CR2032.
2. Why thickness matters
Most devices have a flat plate on one side and a spring on the other. A battery that’s too thin may not reach both, so the device sees no power at all.
3. How to tell which you need
Read the code on the old battery. If it’s worn away, measure the battery you’re replacing with a ruler or caliper and match the thickness.
4. If you buy the wrong one
A CR2025 in a CR2032 slot may fit but not work. A CR2032 in a CR2025 slot is too tall for the case to close. Neither is dangerous, just frustrating.
5. The wider coin cells
A CR2450 is 24.5 mm across and 5 mm thick, so it won’t drop into a 20 mm slot at all. It goes in bigger key fobs and remotes.