Our Roof Pitch Calculator helps contractors, roofers, and DIYers determine roof slope in multiple formats. Calculate pitch as a ratio (e.g., 6:12), angle in degrees, slope percentage, and rafter length. Whether you're estimating materials, planning drainage, or building a new roof, this tool provides all the measurements you need for accurate construction.
Choose whether you know rise/run, pitch ratio, or angle
Input rise and run, pitch (X:12), or angle in degrees
Enter total building width for rafter and area calculations
Include eave overhang for total rafter length
See pitch, angle, rafter length, and roof area
Roof pitch is the ratio of vertical rise to horizontal run. A 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. The angle in degrees is calculated using arctangent. Rafter length uses the Pythagorean theorem.
Pitch = Rise ÷ Run, Angle = arctan(Rise ÷ Run), Rafter = √(Rise² + Run²)
Standard residential roofs range from 4:12 to 9:12 pitch - steeper slopes shed water and snow better
A 4:12 pitch (18.43°) is the minimum recommended for standard asphalt shingles
Measure rise and run in the same units (both inches or both feet) for accurate calculations
Low-slope roofs (below 3:12) require special roofing materials like rolled roofing or membrane
Steeper pitches (above 9:12) may require roof jacks or scaffolding for safe installation
When measuring existing roofs, use a 12-inch level and measure the rise at the 12-inch mark
Roof pitch — the steepness of a roof expressed as a ratio of vertical rise to horizontal run — is one of the most fundamental measurements in residential and commercial construction. A pitch of 6/12, for instance, means the roof rises 6 inches for every 12 inches of horizontal span, which translates to a 26.57-degree angle. Pitch determines everything from material selection to structural load capacity. Low-slope roofs (below 3/12) typically require membrane or built-up roofing systems since standard shingles cannot prevent water infiltration at shallow angles. Standard-slope roofs (4/12 to 9/12) accommodate asphalt shingles, the most common residential material in North America. Steep-slope roofs (10/12 and above) shed snow and rain efficiently but increase material costs and require additional safety measures during installation. Building codes in snow-prone regions often mandate minimum pitch requirements — typically 6/12 or steeper — to prevent dangerous snow accumulation. Accurate pitch calculation also determines rafter length, which directly affects lumber ordering and framing costs. Whether you are planning a new build, re-roofing, or adding a dormer, knowing your exact roof pitch is the starting point for accurate material estimates and code compliance.
Roof pitch describes the steepness of a roof as a ratio of rise to run. A 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance. Understanding pitch is essential for material selection, drainage planning, and structural design.
Low slope (1:12 to 3:12): Requires membrane roofing. Conventional (4:12 to 9:12): Standard for most homes, works with asphalt shingles. Steep slope (10:12+): Better snow shedding, more dramatic appearance, requires safety equipment for installation.
Different roofing materials have minimum pitch requirements. Asphalt shingles: 4:12 minimum (2:12 with special underlayment). Metal roofing: 3:12 minimum. Clay/concrete tiles: 4:12 minimum. Membrane/built-up: Works on flat to low slope.
Data sourced from trusted institutions
All formulas verified against official standards.