Road Grade Calculator
Calculate signed road grade from endpoint elevations and horizontal distance, or estimate the ending elevation from a specified constant grade.
Calculate the average signed grade between two road-profile elevations, or find the ending elevation along an assumed constant grade. The results include the equivalent angle and straight sloped distance, so horizontal stationing stays separate from distance along the surface.
How to use this tool
- Choose whether the unknown is grade or ending elevation.
- Select metres or international feet for every distance and elevation.
- Enter the starting elevation and a positive horizontal station distance.
- Supply the other endpoint elevation or a signed percent grade, then inspect the change in elevation.
Formula
grade (%) = 100 × (ending elevation − starting elevation) / horizontal distance
For the reverse calculation, ending elevation = starting elevation + grade × horizontal distance / 100. The angle is atan(grade / 100). Straight sloped distance follows the right-triangle relation using horizontal distance and elevation change. All elevations must refer to the same datum.
Example
A road profile rises from 100 m to 110 m over 200 m horizontally. Its grade is 100 × 10 / 200 = 5%, and its angle is about 2.862405°. The straight segment length is about 200.249844 m.
Frequently asked questions
Can I enter distance from a vehicle odometer?
Only if it represents the horizontal distance required here. Surface travel distance includes slope and may follow curves; using it directly can understate grade.
Does a negative result mean the inputs are wrong?
No. It means the ending elevation is below the starting elevation in the direction you selected. Reversing endpoints reverses the grade sign.
Is the average grade the steepest section?
No. Intermediate rises and falls can be much steeper. This endpoint calculation does not check vertical curves, drainage, accessibility limits, speed or any local road design requirement.
Sources
Last updated: 2026-10-30