When I first turned on my Pixel XL one of the first frustrations was the fact that it wasn't very obvious as to how to enable the battery percentage. I actually had started to search for a root mod since I couldn't find the option in my settings. My good friend @BaneTech decided to shed some light on the situation for me. I had forgotten that on stock android you have to enable the system ui tuner to add the battery percentage. You do that by pulling down the status bar and then long pressing the settings gear. From the System UI settings you can turn on the battery percentage.
via Bane-Tech.com