Rise Over Run Calculator

This rise over run calculator converts measured rise and run into slope, angle, percent grade, and roof pitch in one step. Choose your input method, enter your numbers, and read all conversion results at once.

1. Select your input method. Choose "Rise and run" if you measured vertical and horizontal distances. Use "Two points" for graph or survey coordinates. Choose "Known angle" or "Known grade" to reverse-calculate rise and run from an existing measurement.
2. Enter rise and run using the same real-world unit. If your rise is in inches, your run should be in inches too. Mixed units produce incorrect slope results.
3. For graph problems, enter the coordinates of two points (X1, Y1) and (X2, Y2). The calculator finds rise as Y2 minus Y1 and run as X2 minus X1 automatically.
4. Click "Calculate slope" to see the slope ratio, decimal slope, percent grade, angle in degrees, and pitch in 12.
5. Use percent grade for roads and ramps. Use pitch in 12 for roof framing. Use angle in degrees for saw cuts and layout angles.

Pro tip: always measure horizontal run, not the diagonal board length. Measuring along the slope instead of the level ground is one of the most common field mistakes and changes the slope result significantly.

Common slope quick reference

Use this table to sanity-check your rise over run calculation. It covers typical slopes for roofs, stairs, and ramps.

The rise over run formula divides vertical change (rise) by horizontal change (run) to produce slope. From that single number, the calculator converts to every other format you might need for construction, grading, or graphing.

Slope = Rise / Run. Both measurements must use the same unit. This rise over run calculator works in feet, inches, or any consistent unit. If rise is 6 inches and run is 24 inches, slope = 6 / 24 = 0.25.

Percent grade = Slope × 100. A 0.25 slope is a 25% grade. Roads and ramps commonly use percent grade for specifications.

Angle = atan(Slope) × (180 / π). A 0.25 slope converts to about 14.04 degrees. Use degrees to convert rise over run into saw cuts, layout angles, and CAD work.

Pitch in 12 = Slope × 12. A 0.25 slope is a 3 in 12 pitch. Roofers and framers read pitch as inches of rise per 12 inches of horizontal run.

Worked example

Given: 6 inches of rise over 24 inches of run.

• Slope = 6 / 24 = 0.25
• Percent grade = 0.25 × 100 = 25%
• Angle = atan(0.25) × (180 / π) = 14.04 degrees
• Pitch in 12 = 0.25 × 12 = 3 in 12

This means the surface rises 3 inches for every 12 inches of horizontal distance. For a roof, that's a relatively gentle slope. For a ramp, it's much steeper than ADA's maximum 1:12 (8.3%) guideline.

Quick rule

• Slope = Rise / Run (same units required)
• Multiply slope by 100 for percent grade
• Multiply slope by 12 for roof pitch in 12

Two-point method (graph use)

For coordinates, rise = Y2 minus Y1 and run = X2 minus X1. Points (3, 2) and (7, 5) give rise = 3 and run = 4, so slope = 3 / 4 = 0.75. Keep the sign consistent: always subtract in the same direction to avoid flipping the slope. Note that run over rise gives the inverse (4 / 3 = 1.33), which some graphing problems use for horizontal distance per unit of vertical change.

Common mistakes this calculator helps prevent

Measuring the diagonal board length instead of the horizontal run is the most common field error. The diagonal is always longer than the run, so using it gives a slope that's lower than the actual incline.

Mixing units is another frequent mistake. If rise is in inches and run is in feet, your slope will be off by a factor of 12. Convert both to the same unit before dividing.

For stairs, total rise and total run give the overall pitch, but individual riser height and tread depth still need separate checks against local building codes.

Assumptions and limitations

This rise over run calculator assumes a straight-line slope. It does not account for curves, transitions, or compound angles. Roof pitch results use standard X in 12 notation and assume a uniform slope. For ramp projects, percent grade helps compare incline, but accessibility compliance requires project-specific code review. Always verify field measurements before cutting or building.