Roof Pitch Calculator
Convert rise and run, an angle, or slope % to roof pitch and a multiplier.
Know your house length and width? Start with the Roofing Calculator →
Convert rise and run
Results update as you type. Nothing is stored on a server.
How to calculate roof pitch
Enter a measurement
Use rise and horizontal run in inches, or switch to Angle or Slope %.
Read the conversion
Get pitch per 12 inches of run, angle, slope percent, and multiplier.
Use the result
Copy or print it, or continue to roof area and bundles with your pitch.
Roof pitch conversions
Use this roof slope calculator as a roof angle calculator to convert roof pitch to degrees, slope percent, and a roof pitch multiplier.
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 4/12 | 18.4° | 33.3% | 1.054 |
| 6/12 | 26.6° | 50.0% | 1.118 |
| 8/12 | 33.7° | 66.7% | 1.202 |
| 12/12 | 45.0° | 100.0% | 1.414 |
- Pitch
- Vertical rise for every 12 units of horizontal run.
- Angle
- The roof’s inclination above horizontal, in degrees.
- Slope
- Rise divided by run, expressed as a percentage.
- Multiplier
- Converts horizontal projected area to sloped area for one uniformly pitched section.
100% slope means 45°, not a vertical roof. Run is horizontal distance, not the sloped roof length.
Pitch ratio and measurement units
An X:12 pitch states the rise for every 12 units of horizontal run. A 6-inch rise over a 12-inch level run is a 6/12 pitch. The ratio is unitless when rise and run use the same unit. This calculator uses inches for rise, run, overhang, and rafter length, so convert field measurements to inches before entering them.
Convert roof pitch to degrees and percent
Degrees = arctan(rise / run) × 180 / π. Slope percent = rise / run × 100. A plan, digital level, or angle finder may report an angle instead of an X:12 ratio; enter that angle in Angle mode. Small rounding differences are normal when converting between formats.
How the roof pitch multiplier works
Multiplier = √(1 + (rise / run)²). Multiply horizontal projected area by this factor only when the area and pitch describe the same uniformly pitched roof section. Measure dormers, intersecting sections, and irregular outlines separately. Material waste, laps, cuts, openings, and installation requirements are separate from this geometry.
Use the Roof Area Calculator for sloped area. See the calculation methodology for formulas and assumptions.
How to measure roof pitch
- From a safely accessible attic, hold a level horizontally with one end against the underside of a rafter.
- At the 12-inch mark, measure vertically up to the rafter. That gap is the rise.
- Enter that rise with a 12-inch run. For a different measured run, enter both actual measurements in inches.
Do not climb onto a roof just to use this calculator. If access is unsafe, use drawings or a qualified professional.
Measurement checks and limitations
Keep the run level, measure the rise at a right angle, and use the same unit for both. On a simple centered gable, one roof-side run is often half the wall-to-wall span; verify the actual wall-to-ridge geometry. Add overhangs separately. Do not use the full building width as the run for one side, or reverse rise and run.
The rafter result is straight-line geometry, not structural sizing. It does not include ridge, seat, or plumb cuts. Verify dimensions, loads, fastening, and code requirements before ordering or building. Leave direct measurement to a qualified professional if a roof is damaged, wet, icy, unusually steep, or near power lines.
Roof pitch calculator FAQ
These answers explain how roof pitch relates to slope, angle, gradient, and multiplier conversions.
How do I calculate roof pitch?
Measure the vertical rise over a 12-inch horizontal run. If the roof rises 6 inches in those 12 inches, the pitch is 6/12. This calculator also converts that ratio into degrees, percent slope, and a pitch multiplier.
What is a 6/12 roof pitch?
A 6/12 pitch rises 6 inches for every 12 inches of run. That is about 26.6 degrees, a 50% slope, and a 1.118 pitch multiplier. It is a common conventional residential pitch in the United States.
How do I convert roof pitch to degrees?
Degrees = arctangent(rise ÷ run) × 180 ÷ π. A 6/12 pitch is arctangent(0.5), which is 26.6 degrees. You can also enter degrees here and get the equivalent X:12 ratio.
What is a pitch multiplier?
The pitch multiplier converts a horizontal footprint into sloped roof area: multiplier = √(1 + (rise ÷ run)²). Multiply the building’s projected area by this factor to estimate actual roof surface.
Is roof pitch the same as roof slope or roof gradient?
They describe the same geometry in different units. Pitch is usually X-in-12, slope is often a percentage, and gradient or angle is degrees. This page keeps all three in sync so you do not need separate calculators.
What counts as a low, conventional, or steep slope?
This tool labels under 2/12 as flat, 2/12 to under 4/12 as low slope, 4/12 through 9/12 as conventional, and above 9/12 as steep. Manufacturer and code limits still govern which materials you can install.