Technical Free

Landscape Grade & Slope Calculator

Calculate slope percent, angle, or vertical rise for grading, drainage, and ADA compliance. Includes drainage recommendations.

Results

Slope %
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Angle
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Ratio
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Rise / Run
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Common Slope References

Min drainage: 0.5% (1:200)
Typical drainage: 2-5%
ADA max ramp: 8.33% (1:12)
Erosion risk: > 25%
Mowable limit: ~33% (3:1)
Retaining wall needed: > 50%
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How to Use This Calculator

1. Choose your calculation mode. Enter rise and run directly, or enter a known slope percentage or angle to find the other values.

2. Select units. Use feet for larger distances or inches for precision grading work.

3. Enter your measurements. The calculator instantly converts between slope percentage, angle in degrees, and ratio format.

How Slope Calculation Works

Slope is expressed three ways in landscaping. All describe the same grade from different perspectives:

Slope % = (Rise / Run) x 100

Angle = arctan(Rise / Run) x (180 / pi)

Ratio = 1 : (Run / Rise)

A 2% slope is the minimum for water to flow reliably across a surface. For landscape drainage, 2-5% is the target range. The ADA maximum for accessible ramps is 8.33% (1:12). Slopes above 25% require erosion control, and slopes above 33% are generally too steep to mow safely.

When Landscape Pros Use This

Grading for drainage. Ensure water flows away from structures at the proper rate. Too flat and water pools; too steep and it erodes the soil.

ADA compliance. Verify walkways and ramps meet the 1:12 maximum slope requirement before pouring concrete or laying pavers.

Retaining wall design. Determine if a slope is too steep for planting alone and needs a retaining wall or terracing solution.

Frequently Asked Questions

How do I calculate slope percentage?
Slope percentage equals rise divided by run, multiplied by 100. If the ground rises 2 feet over 20 feet, the slope is (2/20) x 100 = 10%.
What is the ADA maximum slope for accessibility?
The ADA maximum slope for accessible ramps is 1:12 (8.33% or 4.76 degrees). Ramp landings are required at the top and bottom, and every 30 feet of ramp length.
What slope is needed for proper drainage?
Minimum drainage slope is 0.5%. Adequate drainage for most landscaping is 2-5% slope away from structures. Slopes above 25% require erosion control measures.
How do I convert slope percentage to degrees?
Use the formula: Degrees = arctan(Slope% / 100) x (180 / pi). Common conversions: 5% = 2.86 degrees, 10% = 5.71 degrees, 20% = 11.31 degrees, 100% = 45 degrees.

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