What is rise over run?

Rise over run is the ratio of vertical height (rise) to horizontal distance (run) of any sloped surface. It expresses how steep a slope is. For stairs, a 7.5-inch rise over a 10-inch run means each step goes up 7.5 inches for every 10 inches forward. The ratio can be expressed as a fraction (7.5/10 = 0.75), a percentage (75%), or an angle (36.87 degrees).

How do you calculate rise and run for stairs?

Measure the total vertical distance (total rise) from finished floor to finished floor. Divide by the ideal riser height (7 to 7.75 inches) to get the number of risers. The actual rise per step equals total rise divided by the number of risers. The run per step is the horizontal tread depth, which must be at least 10 inches per IRC code. Total run equals the number of treads (risers minus one) multiplied by the run per step.

What is a comfortable rise and run for stairs?

The most comfortable stair dimensions follow the 17-18 inch rule: one riser plus one tread should equal 17 to 18 inches. A 7-inch rise with an 11-inch run (sum = 18) is widely considered the most comfortable. The IRC allows up to 7.75-inch rise with a minimum 10-inch run. Rises below 7 inches feel shallow, while rises above 8 inches feel uncomfortably steep for most people.

What is the rise over run for a ramp?

The ADA requires a maximum slope of 1:12 for wheelchair ramps, meaning 1 inch of rise for every 12 inches of run (8.33% grade, 4.76 degrees). Ramps steeper than 1:12 are not ADA-compliant and may be unsafe for wheelchair users. For short ramps under 6 inches of rise, a slope of 1:8 (12.5%) may be permitted. Commercial parking garages typically use 5% to 6% slopes.

How do you convert rise over run to degrees?

Use the arctangent (inverse tangent) function: angle in degrees = arctan(rise / run) x (180 / pi). For example, a 7.5-inch rise over 10-inch run: arctan(7.5/10) = arctan(0.75) = 36.87 degrees. Most scientific calculators have an arctan or tan-inverse button. You can also use our calculator above to get the angle instantly.

What is the maximum slope for a driveway?

The maximum recommended driveway slope is 15% (about 8.5 degrees), though some municipalities allow up to 25% for short sections. A 10% slope is considered ideal for residential driveways — steep enough for drainage but manageable in icy conditions. For reference, 15% means the driveway rises 15 feet over a 100-foot horizontal run. Heated driveway systems may be required for slopes exceeding 12% in cold climates.

Free Rise Over Run Calculator — Slope, Angle & Ratio (2026)

Rise over run calculator — free slope tool. Get ratio, percentage, angle & description instantly. Works for stairs, ramps & roofs.

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Enter Your Measurements

How to Use This Calculator

1Enter the rise (vertical height) in inches.
2Enter the run (horizontal distance) in inches.
3Click Calculate for slope ratio, percentage, angle, and a description of the slope type.
4Works for stairs, ramps, roofs, driveways, and any inclined surface.

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About This Material

Rise over run is the fundamental measurement for calculating the slope or pitch of any inclined surface. For stairs, the rise is the vertical height of each step and the run is the horizontal depth of each tread. The IRC specifies a maximum riser height of 7-3/4 inches and a minimum tread run of 10 inches, which produces a slope of approximately 37.75 degrees — near the upper limit of comfortable stair climbing. The classic comfort rule states that one rise plus one run should equal 17 to 18 inches (for example, 7.5-inch rise plus 10.5-inch run equals 18 inches). For roof pitch, rise over run is expressed as a ratio per 12 inches of run (for example, 6:12 means the roof rises 6 inches for every 12 inches of horizontal run). For wheelchair ramps, the ADA requires a maximum slope of 1:12, meaning 1 inch of rise for every 12 inches of run (about 4.76 degrees). Driveways should not exceed a 15% slope (about 8.5 degrees) for safe vehicle access. Understanding rise over run helps you verify code compliance, calculate material lengths, and ensure safety for any sloped construction project.

Next Steps:

Stair Calculator →Stair Stringer Calculator →Roof Pitch Calculator →Roof Slope Calculator →

Installation Tips

•Always check rise and run with a level and tape measure after installation — do not rely solely on calculations.
•For stairs, verify that all risers are within 3/8 inch of each other to meet code and prevent tripping.
•Use a digital angle finder tool to confirm slope angles during construction.
•For ramps, check the slope at multiple points along the run — slight foundation settling can change the angle.

Common Mistakes to Avoid

Confusing rise over run with run over rise — rise is always the vertical measurement, run is always horizontal.
Not accounting for finished floor thickness when measuring total rise for stairs.
Using the wrong units — make sure both rise and run are in the same unit (both inches or both feet).
Forgetting that roof pitch uses 12 inches as the standard run, not the actual run of the roof.

Free Rise Over Run Calculator — Slope, Angle & Ratio (2026)

How to Use This Calculator

About This Material

Installation Tips

Common Mistakes to Avoid

Frequently Asked Questions

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