Slope and grade refer to the rate of change in height or elevation over a distance. Grade is often used in reference to roads or railroad tracks. It is extremely important that grades not be too steep as trucks and trains need to be able to climb and descend the roads and tracks safely.

Calculate the rise by subtracting the starting elevation from the ending elevation. If it is a downhill section, this number should be negative. If it is an uphill, this number should be positive.

Calculate the run. Measure the horizontal distance between the starting and ending points. A level can help you measure horizontal distance.

## Sciencing Video Vault

Divide the rise by the run to determine the slope. The steeper the incline or decline, the larger the number will be. If it is downhill, it will be negative. If it is uphill it will be positive.

Multiply the slope by 100 to get the grade. The grade is expressed as a percentage of the slope.

#### Tip

One way to effectively measure horizontal distance is to use a map. Measure the distance between points A and B on the map and use the scale to convert it to actual distance.

#### Warning

When calculating the run, be sure to use the horizontal distance between points A and B, not the distance of the line that connects points A and B (for example, the road going down a hill).