What is a 4/12 roof pitch in degrees?

A 4/12 roof pitch equals 18.43 degrees. This is one of the most common residential pitches, suitable for standard asphalt shingles and most other roofing materials. It represents the minimum slope at which most shingle manufacturers will honor their warranty without requiring special low-slope installation methods.

What is the most common roof pitch?

The most common residential roof pitches range from 4/12 to 9/12. A 6/12 pitch (26.57°) is frequently considered the standard, offering a good balance of water drainage, usable attic space, and material compatibility. Ranch-style homes often use 4/12 to 5/12, while Colonial and Cape Cod styles typically use 8/12 to 12/12.

How do I measure roof pitch from inside the attic?

Hold a 12-inch level horizontally against the underside of a rafter. At the 12-inch mark on the level, measure the vertical distance straight up to the rafter. That measurement in inches is your pitch — for example, 6 inches equals a 6/12 pitch. This is the most accurate method because you can take the measurement in a safe, controlled environment without climbing on the roof surface.

What roof pitch do I need for asphalt shingles?

Most asphalt shingle manufacturers require a minimum 4/12 pitch (18.43°). Between 2/12 and 4/12, you must use special low-slope application methods with additional underlayment per IRC R905.2.7. Below 2/12, asphalt shingles should not be used at all — low-slope membrane roofing (EPDM, TPO, or modified bitumen) is required instead.

How do I convert roof pitch to degrees?

Divide the pitch number by 12, then take the arctangent: degrees = arctan(pitch ÷ 12) × 180 ÷ π. For example, a 6/12 pitch: arctan(6/12) × 57.2958 = 26.57°. A 4/12 pitch converts to 18.43°, and a 12/12 pitch converts to exactly 45°. This calculator performs the conversion instantly for any pitch value.

What is roof area factor?

The roof area factor (also called slope multiplier) converts a flat plan-view area to actual sloped roof area. It equals √(1 + (pitch/12)²). For a 6/12 pitch, the factor is 1.118 — meaning a 1,000 sq ft floor plan needs 1,118 sq ft of roofing material (before waste). This is the single most useful number for ordering shingles, underlayment, and sheathing.

What is the minimum pitch for a metal roof?

Standing seam metal roofs can be installed at a minimum 3/12 pitch, and some manufacturers allow 2/12 with additional sealant at the seams. Exposed-fastener metal panels (such as corrugated or R-panel) typically require a minimum 3/12 pitch. Always check the specific manufacturer’s installation requirements, as minimum pitch varies by panel profile and seam type.

Roof Pitch Calculator — Pitch, Angle & Slope Converter

How to Use the Roof Pitch Calculator

How to Determine Roof Pitch

Roof pitch describes the steepness of a roof as a ratio of vertical rise to horizontal run, expressed over a 12-inch base. A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. Enter any two of the seven values below — pitch, angle, rise, run, slope percentage, diagonal, or roof area factor — and this calculator instantly converts to all seven formats. Whether you are estimating roofing materials, checking code compliance, or verifying field measurements, having every pitch format at your fingertips eliminates manual conversions and reduces costly ordering mistakes.

Measuring Existing Roof Pitch

There are three reliable methods for measuring an existing roof's pitch, depending on your access and comfort level:

From the attic: Place a level against the underside of a rafter so it reads perfectly horizontal. Mark a point 12" from the wall end of the level. Measure the vertical distance from that 12" mark straight up to the underside of the rafter — that measurement in inches is your pitch. A 6" measurement means a 6/12 pitch.
From the roof surface: Place a 12" level directly on the roof surface with one end touching the shingles. Hold the level horizontal and measure the vertical distance from the far end of the level straight down to the roof surface. This method gives the same result as the attic method, but you must be comfortable working on the roof safely.
From the ground: Use a pitch gauge or speed square held at arm's length, or estimate by counting the number of shingle courses visible on the gable end. Alternatively, a digital angle finder with a tilt sensor (like the Leica DISTO D2) can calculate rise and run from a ground-level laser measurement without climbing on the roof.

Understanding the Seven Pitch Formats

This calculator displays all seven formats simultaneously so you never have to convert manually:

Pitch (x/12): Standard construction notation. "6/12" means 6" of rise per 12" of horizontal run. This is the format used on architectural plans, speed squares, and rafter tables.
Angle (degrees): Protractor measurement of the roof slope from horizontal. A 45° angle equals a 12/12 pitch. Useful for setting miter saws and digital angle finders.
Slope percentage: Rise ÷ run × 100. A 6/12 pitch equals a 50% slope. This format is common in civil engineering, grading plans, and drainage design.
Rise & Run: Actual vertical and horizontal measurements from a specific roof section. Enter any two known dimensions and the calculator derives the pitch.
Diagonal per foot: The hypotenuse length per 12" of run — effectively the rafter length per foot. Calculated as √(12² + rise²). For a 6/12 pitch, this is √(144 + 36) = 13.416" per foot.
Roof area factor: Multiply the flat (plan-view) area by this factor to get the actual sloped roof surface area. For a 6/12 pitch, the factor is 1.118 — meaning a 1,000 sq ft floor plan needs 1,118 sq ft of roofing material. This is the most practical output for material estimation.

Pitch-to-Material Compatibility

The pitch of your roof determines which roofing materials are appropriate. Using the wrong material on the wrong pitch can void manufacturer warranties and violate building codes:

Flat (< 2/12): EPDM rubber, TPO membrane, built-up roofing (BUR). Requires a continuous waterproof membrane because water drains too slowly for overlapping materials to shed it reliably.
Low slope (2/12–4/12): Standing seam metal, modified bitumen, roll roofing. Ice & water shield underlayment is required beneath most materials in this range. Most building codes (IRC R905.2) prohibit standard asphalt shingles below 4/12 without special low-slope application methods.
Standard (4/12–9/12): Asphalt shingles, wood shakes, concrete tile, clay tile. This is the range for most residential roofs — materials are widely available, installation is straightforward, and code requirements are standard.
Steep (9/12–12/12): Slate, architectural shingles, standing seam metal. Steeper pitches shed water and snow quickly but require toe boards or roof jacks for worker safety during installation. Additional fasteners may be required per manufacturer specifications.
Very steep (> 12/12): Specialty installation methods required. Mansard roofs, turrets, decorative features, and church steeples often exceed 12/12. Scaffolding or specialized access equipment is essential for safe installation.

Pro Tips

Most building codes (IRC R905.2) require a minimum 2/12 pitch for any roofing material and a minimum 4/12 pitch for standard asphalt shingle installation without special low-slope application techniques.
Roof area factor is your most practical output — multiply your floor plan area by this number to estimate total roofing material needed. For a hip roof, use the full building footprint; for a gable roof, use the footprint plus any overhangs.
When ordering materials, add a 10–15% waste factor on top of the calculated area to account for cuts, breakage, starter strips, ridge caps, and hip/valley trim pieces.
In snow country, steeper pitches (6/12 and above) shed snow load more effectively and reduce the risk of ice dam formation at the eaves. Consider the ASCE 7 ground snow load map for your region when selecting pitch.
Always verify pitch at multiple points along the roof — older roofs may have sagged unevenly, and additions built at different times may have slightly different pitches even when they appear to match visually.

Free Roof Pitch Calculator — Pitch, Degrees & Slope