So, I finally have time to try to simplify this.
Here for all you that didn't get it:

-Move your cursor over the exp bar under your characters picture in the top-left hand corner of the screen.
-Take the number on the left and subtract it from the number on the right.
(ex. 20,000/320,000 your number would be 320,000 - 20,000 = 300,000)
-Look and see what exp you are getting in your fights. (ex. 200)
-Take your first number and divide it by the second number
(ex. 300,000/200 = 1,500)
-Take that number and divide it by 1.8 (ex. 1,500/1.8 = 833.34)
-Take that number and divide it by 60 (ex. 833.34/60 = 13.89)

So using that example it would take you around 14 hours to level up one time

Sorry if you still don't get it there is literally no way I can simplify this more.

Hope this helps,
-balt