Average Amount of Botox Units to Lift Brows?

29 units to 39 units is a reasonable range. This would be enough to treat the area between the eyebrows which normally pulls down on the middle forehead, and the tail of the eyebrow. These areas pull down in opposite vectors from the forehead muscle that wants to pull up. When their motion is inhibited by the Botox, the antagonistic forehead muscle can pull up simulating a lift (although surgery would provide a better result).

If you get your frown muscles injected along with the depressor muscles of the tail of your eyebrows (corrugator muscle and orbicularis muscles), you should see elevation of your eyebrows. This could be achieved with between 25 and 37.5u of BOTOX Cosmetic.
I hope this is helpful for you.