Battery
Why is it my iPhone dropped from 41% when i leave it overnight then when i woke up it decreases to 21%. Considering all internet or data is off and no running apps.
iPhone 11, iOS 14
Question marked as
go to Settings > Battery > Battery Health, what is that value?
(While you're in this menu area.. Best if you have Optimized battery charging turned on)
If the battery health value is below 80% you should replace your battery.
iPhone Battery Replacement - Official Apple Support
Settings > Battery should also show you what is using your battery.
Are you sure your internet/data is turned off?
Do you have poor cellular reception where your phone sits at night?
Here are some links regarding battery usage..
One tip would be, plug in your phone when you go to bed at night and leave it plugged in all night.
iPhone Battery and Performance - Apple Support
About the battery and performance of iPhone 11 and later - Apple Support