Inputs
Example data table
| Segment | Start elevation | End elevation | Horizontal distance | Grade (%) |
|---|---|---|---|---|
| A | 125.0 m | 131.5 m | 250 m | 2.60 |
| B | 210.0 ft | 222.0 ft | 300 ft | 4.00 |
| C | 98.0 m | 92.5 m | 180 m | -3.06 |
Use segments to model varying slopes along the route.
Formula used
- rise = end_elevation − start_elevation (or provided rise)
- grade(%) = (rise / run) × 100
- angle(°) = arctan(rise / run) × 180/π
- 1 in N = 100 / |grade(%)| (if grade ≠ 0)
These outputs help compare design limits, drainage behavior, and vehicle comfort.
How to use this calculator
- Select an input method that matches your measurements.
- Choose metric or imperial units for elevations and distances.
- Enter values for the chosen method, then press Calculate.
- Review percent grade, angle, and 1 in N ratio above.
- Optionally set a grade limit to check compliance quickly.
- Download CSV or PDF for reporting and site records.
Technical guide
Use this tool during planning, staking, and inspection to keep longitudinal slope consistent with your drawings. Enter a maximum grade limit to flag nonconforming segments early, then export results for daily reports and quality records.
1) What road grade means in construction
Road grade expresses vertical change relative to horizontal distance. Crews use it to set string lines, verify subgrade, and check ride quality before paving. A 5% grade means 5 units of rise per 100 units of run, regardless of unit system.
2) Typical grade ranges you will see
Urban streets commonly fall near 0–6% to support drainage and drivability, while short connectors and access drives may reach 8–12% where terrain forces steeper alignments. For temporary haul roads, grades are often managed to reduce wheel slip and erosion.
3) Using segment-by-segment checks
Real alignments rarely hold one constant slope. Split the route into stations or segments, then compute each grade. This highlights crest and sag transitions where comfort and surface drainage change quickly. Segment checks also help locate where additional cut, fill, or regrading is needed.
4) Percent, angle, and 1-in-N ratio
Percent grade is the most common field value. Angle is useful when matching inclinometer readings. The 1-in-N ratio is popular for communicating gentle slopes; for example, 2% is about 1 in 50. This calculator reports all three for fast comparison.
5) Elevations, distances, and measurement quality
Use consistent horizontal distance, not slope distance. If you only have slope distance, reduce it to horizontal using survey methods. A small elevation error can dominate short runs, so confirm benchmark accuracy and instrument setup. Recheck critical ramps with multiple shots.
6) Drainage and cross-slope context
Longitudinal grade affects gutter flow and ponding risk, but cross-slope controls how water leaves the lane. If water must reach an inlet, verify that the combined longitudinal and cross-slope create a reliable flow path. Document both slopes in your site reports.
7) Earthwork implications and material stability
Steeper grades can increase cut-and-fill quantities and reduce compaction efficiency on the lift. For unpaved surfaces, higher grades raise runoff velocity and can trigger rilling. Consider surface treatments, check dams, or temporary diversion to protect fresh grades during storms.
8) Reporting and compliance workflow
After calculation, save outputs for submittals and as-builts. A simple workflow is: measure, compute, compare against your project limit, then export CSV or PDF to attach with inspection notes. Consistent reporting reduces rework and helps close quality checks faster.
FAQs
1) Is a negative grade a problem?
No. Negative grade simply indicates downhill from start to end. Use the sign to understand drainage direction and vehicle approach conditions. Compare the absolute value to your allowable limit.
2) Should I use slope distance or horizontal distance?
Use horizontal distance for percent grade. Slope distance will slightly understate the grade. If you only have slope distance, convert it to horizontal using survey reduction methods.
3) What does “1 in N” represent?
It means one unit of vertical change for N units of horizontal travel. A smaller N is steeper. For example, 1 in 20 equals 5% grade.
4) How accurate do my inputs need to be?
Accuracy depends on run length. Short runs are sensitive to small elevation errors. For ramps and tie-ins, remeasure critical points and average repeated readings to reduce noise.
5) Can I compare metric and imperial results directly?
Yes. Percent grade and angle are independent of units. Only the rise and run values display in your chosen unit. Use the same unit system within a single calculation.
6) Why does my grade differ from an inclinometer reading?
Inclinometers measure angle directly, while grade uses rise over horizontal run. If your distance is not purely horizontal, or points are not aligned, results can differ. Verify measurement geometry and alignment.
7) When should I compute grade in segments?
Use segments whenever the alignment changes slope, such as near driveways, intersections, or vertical curves. Segment grades reveal local steep spots that a single end-to-end calculation can hide.
Measure slope precisely and keep road designs compliant always.