Battery capacity

Batteries are consumables; they lose a little capacity every time they are discharged, then recharged. On average this works out to about a 1% loss for every 25 “full charge cycles”. As one example, if you charge the phone overnight, every night (and that is what you should do; it is a best practice), it starts the day at 100%. If it drops to 20% by the end of the day before you charge it again overnight that counts as 0.8 full charge cycles (20% to 100%), or about 24 full charge cycles per month of use. For this example your battery capacity will lose about 1% per month. Of course, if the end-of-day level is higher than 20% the capacity loss will be a little less, and if it is lower than 20%, or you charge it during the day, the capacity loss will be higher.

If you mean Battery Health, that is an excellent reading. Battery Health varies with usage and all batteries deteriorate over time. You need not worry until battery health reaches 80%, at which time you will need to replace the battery.. Check these links...

iPhone Battery and Performance - Apple Support

Batteries - Maximizing Performance - Apple

Make that “drops 20%” 😏

Corrected!

Thanks Lawrence. I just corrected my error, I meant to say 80%.