Question
How much grade should a lawn have to allow good drainage and how much is excessive?

Answer
Mr. Waight:

Standard grade for hard surfaces is 1 inch drop in eight feet.  That is absolute minimum.

I would recommend at least two inches per eight feet for lawn and more for flower/shrub beds.

I consider too much grade for a lawn to be what is uncomfortable for mowing.  A comfortable grade is one foot of fall in three feet of horizontal measurement.  You may find that you are comfortable with a steeper slope.  Mowing in wet conditions is dangerous on slopes.

Best wishes.