The horizontal distance is often difficult to determine as it is not based on driving distance (including curves in the road). It is based on straight line distance. Calculating grade and steepness change in feet are good for the calculation of inclined planes in mountain areas. Use the below grade percent incline and downgrade calculator to estimate the actual vertical distance change in feet if you know the grade percentage value and the horizontal distance.
This kind of measurements is most commonly used in roadways. For example, Over a 1-mile horizontal distance, and a 1% grade change, the vertical change in feet is 52.8 ft.