Calculate slope, grade percentage, slope angle, rise and run from two known measurements.
Calculate Slope
Slope Results
How to Calculate Slope
Slope describes how much a surface rises or falls over a horizontal distance. It is commonly expressed as a percentage, decimal, ratio or angle.
Grade (%) = (Rise ÷ Run) × 100
Angle = arctan(Rise ÷ Run)
Sloped Length = √(Rise² + Run²)
For example, a rise of 2 m over a horizontal run of 10 m produces a slope of 0.20, or 20%. The corresponding slope angle is about 11.31 degrees.
Slope Percentage and Ratio
A slope percentage compares the vertical rise with the horizontal run. A slope ratio expresses the same relationship in a ratio format.
| Rise | Run | Grade | Approx. Angle |
|---|---|---|---|
| 1 | 20 | 5% | 2.86° |
| 1 | 10 | 10% | 5.71° |
| 1 | 5 | 20% | 11.31° |
| 1 | 4 | 25% | 14.04° |
| 1 | 2 | 50% | 26.57° |
| 1 | 1 | 100% | 45° |
Where Slope Calculations Are Used
Roof Pitch
Roof pitch uses the vertical rise and horizontal run to describe how steep a roof is. Roof measurements are often expressed as a rise over a 12-unit horizontal run.
Ramps and Accessibility
Slope calculations help compare the rise and horizontal length of ramps. Local accessibility requirements should be checked before construction because permitted slopes depend on the project and applicable regulations.
Drainage and Ground Grading
Drainage surfaces need enough fall to move water toward the intended outlet. The required slope depends on the surface, drainage design, materials and local construction requirements.
Roads and Driveways
Engineers and contractors use grade calculations when planning roads, driveways and other sloped surfaces.
Important Slope Calculation Note
Slope Calculator FAQs
What is the formula for slope?
The basic slope formula is rise divided by run. To express it as a percentage, multiply the result by 100.
How do I calculate slope percentage?
Divide the vertical rise by the horizontal run and multiply the result by 100. For example, a 2 m rise over a 10 m run gives a 20% grade.
What does a 10% slope mean?
A 10% slope means the surface changes vertically by 10 units for every 100 units of horizontal distance.
How do I convert slope percentage to degrees?
Use the inverse tangent function: angle = arctan(slope). The calculator performs this conversion automatically.
Is slope the same as grade?
Slope and grade describe the same rise-to-run relationship. Grade is commonly expressed as a percentage, while slope can also be shown as a decimal, ratio or angle.
Can I use this calculator for roof pitch?
Yes. Enter the roof rise and horizontal run to calculate the slope percentage and angle. Roof pitch is often reported using rise over a 12-unit run.
Does the measurement unit affect the slope?
No. Rise and run must use the same unit, but the final slope ratio, percentage and angle remain the same after consistent unit conversion.