1. Most take a CR2032
The CR2032 is the most common car key battery by far. It fits most Toyota, Honda, Nissan, Hyundai, Kia, Chevrolet, GMC, Jeep and Volkswagen keys.
2. Some brands use other sizes
Mazda and many Mercedes-Benz keys use the thinner CR2025. Newer BMW keys use the wider CR2450. Older keys sometimes take a small CR1620 or CR2016.
3. The key type matters
A push-button smart key, a flip key and a key with buttons on the head can use different batteries, even on the same model and year.
4. How to be sure
Open the key and read the code on the old battery. That code is always right, whatever a list says.