Why is my nexus6P battery life draining so fast

[AC Question]

If i charge my at night and the next morning my battery is at 100% but it only lasts for a maximum of 7 hours. At first i thought it was because i use my phone a lot during school so i decided leave my phone at home and I came back from school and started looking through my messages and within 30 minutes my charge dropped 20%. Could u please help me I don't know if its the app or the phone or me

 

[belodion]

Use it normally until the battery is at about 30%, then post a screenshot here of your battery usage stats.
We'll take it from there.