Mine will almost form a straight line on the battery usage graph when not being used. It will drain very little UNLESS there is an app that hasn't stopped running properly and then, that app will drain the battery, sometimes 30-40% in just a few hours.
I've pulled my Note 5 off the charger before just before I left for work and left the phone at home. When I come back, the battery % is at 98% or so eight hrs later.