Question: how do you figure percentage of slope?
Answer: Percent of slope is determined by dividing the amount of elevation change by the amount of horizontal distance covered (sometimes referred to as "the rise divided by the run"), and then multiplying the result by 100. ... 
1,000 divided by 2,000 equals 0.5. ... 
500 divided by 3,000 equals 0.166. ... 
700 divided by 500 equals 1.4.