Roof Pitch Calculator
Convert between roof pitch (x/12), angle in degrees and the multiplier for converting footprint to roof area.
The roof pitch calculator converts between the three ways roof slope gets expressed: x/12 pitch (the US convention), degrees of angle and the multiplier used to convert building footprint to actual roof area. Roofers and shingle manufacturers use pitch; architects and engineers use degrees; the multiplier comes up whenever you are calculating shingles, underlayment or roof paint and only have the floor plan to work from. Enter any one of the three and the calculator returns the others plus the slope category - low slope roofs (under 4/12) often need different roofing materials than conventional slopes.
Explore all our roofing calculator tools, or browse the full construction & home improvement diy calculators.
Frequently asked questions
Use a 12-inch level held perfectly horizontal against the roof underside (in the attic) or roof surface. Measure the vertical distance from the end of the level (12 inches from the roof) down to the roof - that distance in inches is the rise per 12 inch run. A 6 inch drop = 6/12 pitch. For the safest measurement use a digital level or smartphone level app on the roof rafters.
4/12 to 9/12 is the conventional residential range. 6/12 is the most common in modern US construction - steep enough to shed water and snow but shallow enough to install standard shingles safely without scaffolding. Ranch homes from the 1950s-70s commonly used 4/12. Steeper Victorian and Craftsman roofs run 8/12 to 12/12.
A 6/12 pitch equals 26.57 degrees. Other common pitches: 4/12 = 18.43 degrees, 8/12 = 33.69 degrees, 10/12 = 39.81 degrees, 12/12 = 45 degrees. Beyond 12/12 the math reverses - a 24/12 'pitch' is a 63.43 degree wall, not a normal roof slope.
The multiplier converts horizontal footprint area to actual sloped roof area for ordering shingles, underlayment or any material that goes on the roof surface. Formula: sqrt((rise/12)^2 + 1). A 6/12 pitch has multiplier 1.118 - so a 40x30 ft footprint with a 6/12 gable roof has 1,342 sq ft of roof surface (40 x 30 x 1.118). Steeper roofs have bigger multipliers.
Under 4/12 is generally low slope in residential roofing. Under 2/12 is essentially flat and needs a single-ply membrane (TPO, EPDM, modified bitumen) - asphalt shingles will leak. 2/12 to 4/12 can use shingles but with a double underlayment or ice and water shield over the entire roof, not just the eaves. Always check shingle manufacturer specs before installing on a low slope.