Roof Pitch & Roof Area Calculator
Convert rise/run to pitch angle and estimate sloped area for a simple roof from plan dimensions.
Calculate roof pitch, slope factor and roof area
Convert rise/run to pitch angle and estimate sloped area for a simple roof from plan dimensions.
How the roof pitch & roof area calculator works
Pitch slope is rise divided by run. The angle is arctangent of that slope, while the slope factor is √(1 + slope²). Multiplying horizontal plan area by the slope factor estimates the sloped surface area for a simple roof.
Where this construction calculation helps
Use it to translate familiar pitch ratios into degrees and get an early roofing-material area before detailed hip, valley and flashing takeoffs.
Measurements and assumptions
The plan dimensions should reflect the horizontal roof footprint you want covered. Add overhangs if they are part of the roof area. Complex roofs should be divided into individual planes rather than treated as one rectangle.
Worked example
A 6:12 pitch has a slope of 0.5, an angle of about 26.57° and a slope factor of about 1.118.
Distinguish plan area from sloped roof area
A roof pitch and roof area calculator adjusts horizontal plan dimensions for slope so material coverage reflects the inclined surface rather than only the building footprint. The estimate may still need additions for eaves, rakes, hips, valleys, dormers and other roof geometry. Roofing products are commonly purchased in discrete sheets, bundles or tiles, so convert the calculated area using the manufacturer's coverage and add cutting or lap allowance appropriate to the system. Complex roofs should be broken into measurable planes instead of treated as one rectangle.