To determine the slope of land, you need
to know the distance from top to bottom,
and the height of the drop.
Mark off 10 feet of the slope, use this to
determine the slope.
Drive a short stake at the top of the ten
foot area, and run a string between the
upper point and the lower, this is the run.
Tie the string to the top stake, pull it
taunt, level the string with a carpenter
level by raising or lowering the string.
At the lower point, measure the distance
from the string to the ground, this the
Enter these two figures into the calculator,
this will give you the percent of grade.