Roof slope calculator
Convert a roof slope between pitch notation, degrees and percent grade, whichever one you already have.
Roof slope calculator
Convert a roof slope between pitch notation, degrees and percent grade, whichever one you already have.
Enter a value to convert.
Roof pitch
Project summary
How it works
Steepness and pitch descriptions here are general, not building code requirements. Roofing material, ventilation and structural requirements vary by jurisdiction; check local code before building.
Roof slope calculator
Three notations, one slope
Roofers, framers and engineers do not always describe slope the same way: a plan might specify a pitch in x-in-12 notation, a solar panel spec might want degrees, and a drainage calculation might use percent grade. This calculator starts from whichever one you already have and converts it to the other two, rather than making you re-derive them by hand.
How this differs from the pitch calculator
The roof pitch calculator measures a pitch from a rise and a run you supply, useful when you are standing at the roof with a level and tape. This slope calculator instead converts a slope you already know from one notation to the others, useful when a document or spec sheet already states a value in a format you need translated.
Frequently asked questions
What is a 6 in 12 pitch in degrees?
A 6 in 12 pitch is about 26.6 degrees. Enter 6 into the pitch field above to confirm, or enter a different pitch, angle or percent grade to convert it.
What is a 45 degree roof in pitch notation?
A 45 degree roof angle equals a 12 in 12 pitch, also expressed as a 100 percent grade. That is an unusually steep residential roof; most homes fall between about 4 in 12 and 9 in 12.
What is the difference between pitch and slope?
Pitch is the ratio of total rise to total span. Slope is the ratio of rise to run, which is half the span. A roof that rises 8 feet over a 24 foot span has a pitch of 8/24 or 1/3, but a slope of 8/12. The calculator works with slope, which is the standard measurement used in roofing.
How does slope affect roof area?
A steeper slope increases the roof surface area even though the building footprint stays the same. A 12 in 12 slope creates a roof surface about 41 percent larger than the flat footprint. The calculator multiplies your footprint by the slope factor to give you the true roof area for material ordering.
What slope is best for shedding snow?
Slopes above 6 in 12 shed snow well. Slopes below 3 in 12 can accumulate snow and ice, which adds weight and increases leak risk. In heavy snow areas, steeper slopes help but also catch more wind. Your local building code accounts for snow load in the structural requirements.
Can I change my roof slope during re-roofing?
Changing slope requires adding new framing on top of the existing structure, which adds cost and weight. It is sometimes done when converting from flat to pitched or when the existing roof structure has sagged. The calculator works with whatever slope you enter, and you can compare material needs at different slopes.
How do I convert slope to degrees?
The calculator shows the slope angle in degrees automatically. If you need to calculate it manually, take the arctangent of the rise divided by the run. A 6 in 12 slope equals about 26.6 degrees. A 12 in 12 slope equals 45 degrees.
Does slope affect roofing material choice?
Yes. Very low slopes under 2 in 12 require membrane roofing instead of shingles. Moderate slopes from 2 to 6 in 12 can use shingles with special underlayment. Steeper slopes above 6 in 12 work with any standard shingle. The calculator helps you estimate material quantities for your chosen slope.