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Slope Calculator

Calculate slope ratio, rise, run, percentage grade, pitch, angle (degrees and radians), and horizontal distance for roads, driveways, roofs, drainage, and ramps.

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Select a calculation mode and enter dimensions to solve the slope.

Dimension Specifications

Slope Guide Diagram
Angle (θ)Run / Horiz. Dist.RiseSlope Length

Ready to Calculate

Select a calculation mode, enter your specifications, and click Calculate to see the complete slope metrics.

Formula Details

Select a calculation mode above to display its corresponding geometry formula and variables, or browse the specific calculations below:

Calculation Example

Worked Example
Scenario

Residential Roof Pitch: Calculate the diagonal length and angle for a roof with a pitch of 6/12 (Rise = 6 in, Run = 12 in) with a total run of 16 feet.

Calculation Steps
  1. 1.Select Rise & Run mode, change units to Imperial (ft/in).
    Rise = 6 in, Run = 12 in
  2. 2.The calculator determines the unitless slope values first.
    Slope Ratio = 1 : 2 | Grade = 50.00% | Angle = 26.57°
  3. 3.Scale these to the target Run of 16 ft.
    Rise = 16 ft × 0.50 = 8.00 ft | Slope Length = √(8² + 16²) = 17.89 ft
Final Quantity NeededSlope Length: 17.89 ft, Rise: 8.00 ft, Angle: 26.57°
Worked Example
Scenario

Wheelchair Ramp (ADA compliant): A public ramp requires a vertical rise of 2.5 feet. The ADA specifies a maximum slope ratio of 1:12 (8.33% grade). Find the required run and ramp length.

Calculation Steps
  1. 1.Select Slope Ratio mode. Set Ratio Rise = 1, Ratio Run = 12. Set Known Dimension Type = Rise with value = 2.5 ft.
    Ratio = 1 : 12, Rise = 2.5 ft
  2. 2.Calculate the horizontal run distance needed.
    Run = Rise × 12 = 2.5 ft × 12 = 30.00 ft
  3. 3.Calculate the physical ramp slope length.
    Slope Length = √(2.5² + 30²) = 30.10 ft
Final Quantity NeededRequired Run: 30.00 ft, Ramp Length: 30.10 ft, Grade: 8.33%
Worked Example
Scenario

Driveway Slope: A landscaping project requires a driveway to rise 1.8 meters over a horizontal distance of 12 meters. Check if the grade is safe for vehicles.

Calculation Steps
  1. 1.Select Rise & Run mode. Set Rise = 1.8 m, Run = 12.0 m.
    Rise = 1.8 m, Run = 12.0 m
  2. 2.Calculate the grade percentage.
    Grade = (1.8 / 12) × 100 = 15.00%
  3. 3.Compare with typical design guidelines (maximum standard driveway grade is 15% to 20%). The slope is 15.00% (8.53°), which is safe but steep.
    Grade = 15.00% (Within safe limits)
Final Quantity NeededGrade: 15.00%, Angle: 8.53°, Slope Length: 12.13 m

How to Use

Follow these simple steps to solve and convert any slope configuration:

  1. Select the desired calculation mode: Choose from Rise & Run, Angle & Run, Angle & Rise, Slope Length & Rise, Slope Length & Run, Slope Ratio, or Percentage Grade.
  2. Choose the preferred unit system: Toggle between Imperial (ft/in) and Metric (m/cm/mm) at the top right of the calculator card.
  3. Enter the required values: Supply the measurements in the dynamic input fields. Unneeded fields will be automatically hidden based on your mode.
  4. Click Calculate: Click the Calculate button to process the dimensions.
  5. Review the results: Look at the visual angle dial, vertical rise, horizontal run, slope length, ratios, percentage grade, and roof pitch all calculated together in the results section.
  6. Clear fields: Click Reset at any time to clear the form and start a new calculation.

Frequently Asked Questions

What is slope in construction?
Slope measures the steepness of a surface or line relative to the horizontal plane. It is calculated as the vertical rise (height change) divided by the horizontal run (distance change). In construction and engineering, it is expressed as a ratio (e.g. 1:4), a percentage grade (e.g. 25%), an angle in degrees, or a roof pitch fraction (e.g. 4/12).
What is the difference between slope ratio and grade?
Slope ratio compares vertical rise to horizontal run directly (e.g., 1:12 means 1 unit of rise for every 12 units of run). Grade is the same slope relationship expressed as a percentage (e.g., 1/12 ≈ 0.0833, or 8.33% grade). Both describe the same steepness, but different industries prefer one over the other (civil engineering uses ratios/grades, roadways use grades).
How do I calculate roof pitch?
Roof pitch is traditionally measured as the number of inches a roof rises vertically for every 12 inches it runs horizontally. For example, if a roof rises 4 inches over a 12-inch horizontal run, the pitch is 4/12. You can calculate this by measuring the rise and run, normalizing the run to 12, and scaling the rise accordingly: Pitch Rise = (Rise / Run) × 12.
How do I convert slope to degrees?
To convert slope (Rise/Run ratio) to degrees, find the arctangent (inverse tangent) of the slope fraction, and then convert radians to degrees: Angle (Degrees) = arctan(Rise / Run) × 180 / π. For example, a 1:4 slope has a ratio of 0.25, and arctan(0.25) ≈ 14.04°.
What is a safe driveway slope?
Standard design guidelines recommend a maximum driveway slope grade of 15%, though some municipal codes allow up to 20% for short segments. Slopes above 15% can cause vehicles to scrape, lose traction in wet or icy conditions, or feel uncomfortable to park on. A slope of 1% to 5% is optimal for drainage while keeping parking easy.
Can I switch between Metric and Imperial units?
Yes, you can toggle between Imperial (in, ft) and Metric (mm, cm, m) systems at the top of the calculator form. All input fields, placeholders, labels, and output results will instantly convert.

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Disclaimer

Calculations are estimates based on the values you enter and standard engineering formulas. Results are intended for planning and estimation only. Always verify critical measurements, specifications, and local building requirements before purchasing materials or beginning construction.