Why does iPhone 12 Pro battery capacity drop fast

Hello,

These are the standard steps for short battery life:

1) Have you tried a restart?  If not, do it now.

2) Go to Settings > Battery > BATTERY USAGE BY APP to see the apps that are consuming your battery.

3) Check “Battery Health” in the link: 

iPhone Battery and Performance

4) If all else fails, consider a battery replacement:

iPhone Battery & Power Repair

Good luck.