This simple XP Bar Addon is the same XP bar that is within my War Genesis Character Bars addon as well, however, this is a standalone XP bar and hourly XP indicator, in case anybody doesn't want to have the other functionality from the other addon.
The XP per hour indicator is one of the most accurate XP calculators out there (to my knowledge). It has a 5 minute timer, so the closer you get to the 5 minute mark, the more accurate it becomes! (this calculator takes into account gaps between mob kills, turning in quests and such by using 5 minutes. It still calculates quicker, giving you a rough estimate based off your kills, but gets more accurate the longer you go!)
Move the XP bar by going to Settings -> Simple XP and unlocking the frames
Feel free to leave me comments and requests for any changes that you may want!