Slope Percentage Calculator
Calculate slope percentage, grade, and angle conversions for construction and engineering
Calculate Slope Percentage
Positive for uphill, negative for downhill
Horizontal distance covered
Slope Calculation Results
Cannot calculate slope
Run (horizontal distance) cannot be zero
Real-World Slope Examples
ADA Compliant Ramp
Rise: 1m, Run: 12m (8.33% max slope)
ADA requires ramps to have maximum 8.33% slope (1:12 ratio)
Steep Road Grade
Angle: 15° (steep mountain road)
A 15° angle corresponds to a 26.79% grade - very steep for roads
Moderate Hill
Slope: 5% (common road grade)
A 5% slope is moderate, rising 5m over 100m horizontal distance
Roof Pitch
Rise: 4m, Run: 12m (typical roof)
A 4:12 roof pitch equals 33.33% slope or 18.43° angle
Slope Reference Guide
Construction Standards
ADA Ramps: ≤8.33% (1:12)
Maximum allowable slope
Sidewalks: 2-5%
For drainage and accessibility
Roads: 3-12%
Depending on traffic and location
Roof Pitch: 25-100%
For water drainage
Understanding Slope Percentage
What is Slope Percentage?
Slope percentage (also called grade percentage) is a way to express the steepness of an incline. It represents how much the elevation changes over a horizontal distance, expressed as a percentage. For example, a 10% slope means the elevation rises (or falls) 10 units for every 100 units of horizontal distance.
The Formula
Slope % = (Rise ÷ Run) × 100%
Slope % = tan(angle) × 100%
- •Rise: Vertical change in elevation
- •Run: Horizontal distance covered
- •Angle: Angle of incline in degrees
Applications
Construction & Architecture
Essential for designing ramps, stairs, roofs, and drainage systems. Building codes specify maximum slopes for accessibility and safety.
Civil Engineering
Used in road design, railway planning, and surveying. Helps determine feasible routes and construction requirements.
Landscape & Recreation
Important for trail design, ski slope classification, and landscaping projects. Affects accessibility and safety.
Conversion Relationships
Percentage to Degrees
angle = arctan(slope % ÷ 100)
Use inverse tangent function to convert slope percentage to angle
Degrees to Percentage
slope % = tan(angle) × 100
Use tangent function to convert angle to slope percentage
Rise/Run to Percentage
slope % = (rise ÷ run) × 100
Direct calculation from vertical and horizontal measurements
Important Notes
Sign Convention
- • Positive slope: uphill/rising terrain
- • Negative slope: downhill/falling terrain
- • Zero slope: perfectly flat/horizontal
Practical Limits
- • Angles must be between -90° and 90°
- • Slope approaches infinity as angle approaches ±90°
- • 100% slope equals 45° angle