Ok so I tried this last night (sorry for the late response)
I turned my phone off at around 2300 at 76%
I turned my phone back on at around 1100 at 73%
So I received a 3% drop in turning my phone back on.
You might just want to pull your battery for when you go to sleep and put it back in afterwards. I'm not sure if you have a defective battery or what. The only reason that I think this could be happening for you is that your battery power is still running a circuit in your phone even when it's off, it's not using juice for anything but the power moving in a circuit is still draining battery life. That's as far as I could tell from my old high school physics class years ago.