Hill Slope Calculator

Compute hill slope from rise and run with confidence. See percent grade, angle in degrees, and grade ratio. Mix and match units for rise and run independently. Export CSV or PDF, then share results easily. Color classes flag terrain difficulty clearly for quick judgment.

Inputs
Use negative for downhill if desired.
Formula Used
  • Percent grade: % = (rise / run) × 100
  • Angle: θ = arctan(rise / run) in degrees
  • Grade ratio: 1 : N, where N = run / |rise|
  • Slope length: L = √(rise² + run²)
Rise and run are converted to a common unit internally.
Grade Class Map
Ranges are by absolute percent grade; color shows class.
  • Gentle: < 5%
  • Moderate: 5%–<10%
  • Steep: 10%–<20%
  • Very Steep: 20%–<35%
  • Extreme: ≥ 35%
Results
Legend:
Percent grade
Angle (deg)
Grade ratio
Slope length
Classification:

Saved Scenarios
# Rise Rise Unit Run Run Unit % Grade Angle (°) Ratio Slope Length
Example Data Table
Rise Rise Unit Run Run Unit % Grade Angle (°) Ratio Slope Length
30m0.2km 15.00%8.53°1:6.67202.24 m
12ft100ft 12.00%6.84°1:8.33100.72 ft
-25m300m -8.33%-4.76°-1:12.00301.04 m
Grade–Angle–Ratio Cheatsheet
% GradeAngle (°)Ratio (1:N)
2.00%1.15°1:50.00
5.00%2.86°1:20.00
8.33%4.76°1:12.00
10.00%5.71°1:10.00
12.00%6.84°1:8.33
15.00%8.53°1:6.67
20.00%11.31°1:5.00
25.00%14.04°1:4.00
33.33%18.43°1:3.00
50.00%26.57°1:2.00
75.00%36.87°1:1.33
100.00%45.00°1:1.00
Rise per 100 Run Units
% GradeRise per 100 (same units)
2.00%2.00
5.00%5.00
8.33%8.33
10.00%10.00
12.00%12.00
15.00%15.00
20.00%20.00
25.00%25.00
33.33%33.33
50.00%50.00
75.00%75.00
100.00%100.00
Common Unit Conversions
  • 1 meter = 3.28084 feet
  • 1 foot = 0.3048 meters
  • 1 kilometer = 0.621371 miles
  • 1 mile = 1.609344 kilometers
  • Ratio 1:N → % = 100 / N
  • % → ratio N = 100 / %
  • % → angle (°) = atan(%/100) × 180/π
  • Angle (°) → % = tan(°) × 100

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.