Roof Pitch Chart: Slope to Degree Conversion + Calculator

By The Roofing Brief Team. Last reviewed: October 2026.

A roof pitch chart converts the X/12 rise/run format used by builders to the degree angle and percentage slope formats used by architects, engineers, and code officials. A 6/12 pitch is 26.57 degrees and 50 percent slope, and a 12/12 pitch is 45 degrees and 100 percent. Related: Pitch calculator method.

The Complete Pitch Chart: 1/12 Through 24/12

Pitch (X/12)	Angle (Degrees)	Percent Slope	Slope Category
1/12	4.76	8.33	Low slope (membrane required)
2/12	9.46	16.67	Low slope (special details)
3/12	14.04	25.00	Conventional slope
4/12	18.43	33.33	Conventional slope (asphalt min)
5/12	22.62	41.67	Standard slope
6/12	26.57	50.00	Standard slope (very common)
7/12	30.26	58.33	Standard slope (walkable limit)
8/12	33.69	66.67	Standard slope (roof jacks)
9/12	36.87	75.00	Steep slope (specialty labor)
10/12	39.81	83.33	Steep slope
11/12	42.51	91.67	Steep slope
12/12	45.00	100.00	Steep slope
13/12	47.29	108.33	Steep slope
14/12	49.40	116.67	Steep slope
15/12	51.34	125.00	Steep slope
16/12	53.13	133.33	Steep slope
17/12	54.78	141.67	Steep slope
18/12	56.31	150.00	Steep slope
19/12	57.72	158.33	Very steep
20/12	59.04	166.67	Very steep
21/12	60.26	175.00	Very steep (specialty)
22/12	61.39	183.33	Very steep (specialty)
23/12	62.45	191.67	Very steep (specialty)
24/12	63.43	200.00	Very steep (specialty)

How Roof Pitch Is Measured

Roof pitch is measured at any point on the roof slope by establishing a level run line and measuring the vertical drop to the roof plane below. The standard run distance is 12 inches, with the rise expressed in inches over that same 12-inch run. A 6/12 pitch rises 6 inches over a 12-inch horizontal run. The measurement is taken with a level held horizontally against the roof, a ruler or framing square measuring the rise, and a string line or chalk line marking the slope plane.

Pitch is constant across a single roof plane but varies between planes on multi-pitch roofs, and IRC R905.2.2 applies to each plane’s own pitch. A home with a 6/12 main gable and a 3/12 porch addition has two pitches. Both pitches matter for material selection because the lower pitch may not warrant the same shingle product.

Rise Over Run: The X/12 Format

The X/12 format is the builder shorthand used in the United States and Canada. The 12-inch run is the constant denominator (chosen because most framing squares have a 12-inch leg), with X representing the rise. The format is read aloud as “X in 12” or “X to 12.” A 4/12 pitch is read as “four in twelve.” Internationally, pitch is more often expressed as degrees or as a 1:N ratio (a 4/12 pitch is 1:3 in the European 1:N format).

Converting to Degrees: The Arctangent Formula

The conversion from X/12 to degrees uses the inverse tangent (arctangent) function. The formula is: degrees = arctan(X divided by 12). A 6/12 pitch converts as: arctan(6/12) = arctan(0.5) = 26.57 degrees. The conversion is symmetric: a 12/12 pitch is exactly 45 degrees because the rise equals the run, and the tangent of 45 degrees is 1.0.

The chart above covers integer pitches from 1/12 through 24/12; interpolate between rows for 4.5/12 or 7.5/12.

Converting to Percent Slope

Percent slope is the simpler conversion: percent slope = (X divided by 12) times 100. A 6/12 pitch is 50 percent slope. A 12/12 pitch is 100 percent slope (not 100 degrees). Percent slope is the format used in road and grading work, in ADA accessibility calculations, and in commercial roofing specifications. The format is intuitive once you internalize that 100 percent means a 45-degree angle, not vertical.

Low Slope (Below 2/12): Membrane Required

Pitches below 2/12 are classified as low slope by the IRC and most material manufacturers. Shingle products are not rated for this range because the shallow slope allows water to pond, wicks behind exposed fastener lines, and ages the material at accelerated rates. Low-slope roofs require membrane systems: modified bitumen, TPO, EPDM, PVC, or built-up roofing (BUR). The breakdown for two common membrane categories is at the modified bitumen and TPO articles published elsewhere in The Roofing Brief. Code reference: IRC R905.2.2 allows asphalt shingles only on 2/12 or steeper.

Conventional Slope (2/12 to 4/12): Material Restrictions

The 2/12 to 4/12 range is where asphalt shingles become technically allowable but with restrictive detailing. IRC R905.2.2 permits asphalt shingles on pitches as low as 2/12, and requires double underlayment from 2/12 up to 4/12 (2021 Seattle Residential Code chapter 9). Maker instructions can add detailing at low pitch, so read the install sheet for the specific line before relying on its warranty. Single-layer synthetic underlayment applies from 4/12 up.

Standard Slope (4/12 to 9/12): Most Asphalt Shingles

The 4/12 to 9/12 range is the sweet spot for residential roofing. Asphalt shingles install with full warranty terms. The slope sheds water and snow effectively without creating walkability hazards. The architectural proportions are pleasing for most house styles. The 6/12 pitch is the most-common residential pitch in the United States, balancing material economy, weather performance, and architectural proportion. The 5/12 and 7/12 pitches are nearly as common, particularly in regional styles (5/12 common in southern markets, 7/12 in northern markets and snowbelt states).

Steep Slope (9/12 to 21/12): Walkability Concerns

Pitches from 9/12 to 21/12 require roof jacks, toe boards, or fall-arrest systems for safe access. Labor costs more than on standard-slope work because the install pace slows, scaffolding may be required, and OSHA fall-protection compliance adds setup time; our 2026 roofing cost report adds $1 to $4 per sq ft for steep-pitch surcharges. Material choice expands at steep slopes: slate, cedar shake, and decorative tile become architecturally appropriate, and the steep slope makes the visual texture of these materials more apparent from the street.

Very Steep (Above 21/12): Specialty Work

Pitches above 21/12 (above 60 degrees) approach vertical and are treated as wall cladding from an installation standpoint. The 18/12 and steeper pitches appear on Mansard roofs (the steep lower slope is often 18/12 to 22/12), Victorian turrets, Gothic Revival churches, and modern-architectural angular roofs. Specialty fall-protection equipment and rigging are required, and the labor surcharge sits above the $1 to $4 per sq ft steep-pitch range in the cost report. The mansard roof geometry is the most-common context for very-steep pitches. For asphalt shingles above 21/12, the maker’s steep-slope fastening method applies; see our A-frame roof pitch and steep-slope shingle rules.

Material Compatibility by Pitch

Material	Minimum Pitch	Maximum Pitch	Sweet Spot
EPDM membrane	1/4 in 12 (essentially flat)	12/12	1/12 to 4/12
TPO membrane	1/4 in 12	12/12	1/12 to 4/12
Modified bitumen	1/4 in 12	6/12	1/12 to 4/12
Built-up roofing (BUR)	1/4 in 12	3/12	1/12 to 3/12
Asphalt shingles (special)	2/12	21/12 normal application; steep-slope method above	4/12 to 12/12
Asphalt shingles (standard)	4/12	21/12 normal application; steep-slope method above	5/12 to 9/12
Standing seam metal (mech seam)	1/4 in 12	No limit	3/12 to 12/12
Standing seam metal (snap lock)	3/12	No limit	4/12 to 12/12
Corrugated metal through-fastener	3/12	No limit	4/12 to 9/12
Concrete or clay tile	2.5/12 (special)	21/12	4/12 to 7/12
Natural slate	4/12	21/12	6/12 to 12/12
Cedar shake	3/12 (IRC R905.8.2); 4/12 in the IBC	No code maximum listed	5/12 to 10/12

The 21/12 figure is the largest slope ARMA considers suitable for normal asphalt shingle application; above it, the maker’s steep-slope fastening and cement spots apply (ARMA). It is a method change, not a prohibition.

Code Minimums by Material (IRC R905 References)

The International Residential Code Section R905 governs material-specific roofing installation. R905.1.1 sets underlayment requirements for every covering. R905.2.2 sets the asphalt shingle minimum at 2/12, with double underlayment from 2/12 up to 4/12. R905.10.2 sets metal panel minimums: 3/12 for lapped, nonsoldered-seam panels without lap sealant, 1/2 in 12 with applied lap sealant, and 1/4 in 12 for standing seam systems. R905.3.2 sets clay and concrete tile at 2.5/12 or steeper, with double underlayment up to 4/12. R905.7.2 and R905.8.2 set wood shingles and shakes at 3/12. Section numbers were checked against the 2021 Seattle Residential Code chapter 9, which tracks the 2021 IRC; confirm your jurisdiction’s adopted edition in IRC Chapter 9.

Decision table: what your pitch allows

If your pitch is	Then
Below 2/12	Use a membrane (modified bitumen, TPO, EPDM); asphalt shingles are not allowed (R905.2.2)
2/12 up to 4/12	Asphalt shingles need double underlayment (R905.2.2); tile needs 2.5/12 or steeper (R905.3.2)
4/12 to 9/12	Standard asphalt install with single underlayment
Above 4/12 (any roofer on the roof)	OSHA steep-roof rules: guardrails, nets or personal fall arrest at 6 feet or more
Above 21/12 with shingles	Maker steep-slope method: extra fasteners plus cement spots under the tabs
Standing seam metal at 1/4 in 12 to 3/12	Standing seam allowed down to 1/4 in 12 (R905.10.2); lapped panels need 3/12 without sealant
Wood shakes or shingles	3/12 minimum under the IRC; 4/12 for shakes under the IBC

How to Measure Pitch on Your Own Roof

Three methods give an accurate roof pitch measurement without climbing onto the roof itself. First, the attic method: place a 12-inch level horizontally against the underside of a rafter, mark the point 12 inches along the level, then measure the vertical distance from that point up to the rafter underside. That vertical distance is the X in X/12. Second, the gable-end method: from inside or outside, measure the horizontal width of the gable and the vertical height from the top plate to the peak. Pitch = (height divided by half the width) times 12. Third, the smartphone app method: smartphone tools like Pitch Gauge, Klein Tools Bubble Level, and the iOS Measure app use the device gyroscope to read the angle of a flat surface; the app reads the slope when held against any roof plane.

Pitch and Wind Performance

Pitch changes wind uplift on the panels and shingles, but not in one direction. ASCE 7 publishes separate roof pressure coefficients by slope band, so the pitch changes the design uplift on each roof zone and steeper is not automatically lower. Steeper pitches also have larger sail area at the gable end, increasing lateral loads on the framing and wall anchorage. Full hurricane-zone discussion at best roof for hurricane.

Pitch and Snow Load

Steeper pitches shed snow faster and reduce ground snow load on the roof. A 4/12 pitch holds snow in cold conditions, accumulating toward the full ground snow load value, while a 12/12 pitch sheds most of it, with snow guards or rails required to prevent rooftop avalanches over doorways and walkways. The IRC and ASCE 7 reduce the calculated snow load for steeper-pitched roofs through a slope factor (Cs) that decreases linearly from 1.0 at 30 degrees (roughly 7/12) to 0.0 at 70 degrees (roughly 33/12).

Pitch and Material Lifespan

Water sheds faster off a steeper asphalt roof, which reduces wet-time UV damage and granule loss, and installs below 4/12 need double underlayment under IRC R905.2.2. Read the maker’s warranty for the slope range it covers. The full lifespan discussion is at how long does a roof last.

Pitch and Roofing Cost

Pitch affects total roof cost ($1 to $4 per sq ft of steep-pitch surcharge in our 2026 roofing cost report) through three mechanisms: surface area (steeper roofs have more square footage to cover for the same building footprint), labor pace (steeper roofs install more slowly), and material waste (steeper roofs sometimes generate more cutting waste at hip and valley intersections). The square-footage multiplier is calculable: a 6/12 pitch roof has 1.118 times the surface area of the building footprint, while a 12/12 pitch roof has 1.414 times. Labor pace slows on steep slopes, accelerating above 9/12. Roofing cost data including the pitch multipliers is at how much does a new roof cost. For changing the slope of an existing roof, see what it costs to raise a roof pitch.

Pitch and Ventilation

Steeper-pitched roofs have a slight ventilation advantage from the stack effect: warm air in the attic rises faster through a steeper geometry, increasing the air change rate through ridge and soffit vents. The effect is small, and proper ventilation design dominates the actual performance. The complete ventilation discussion is at attic ventilation. The IRC R806 minimums (1 to 150 or 1 to 300 net free area ratios) apply equally across all pitches.

Pitch and Solar Panel Performance

Solar PV panels perform best at a tilt angle approximately equal to the site latitude for year-round generation, or angle minus 15 degrees for summer-peak generation. For a 40-degree latitude site (Denver, Philadelphia, Indianapolis), the optimal panel tilt is 40 degrees, which converts to approximately a 10/12 roof pitch. Solar installers often add tilt brackets on shallower-pitched roofs to bring the panel angle closer to optimum, at the cost of extra brackets and wind-load engineering; ask the installer for a modeled production comparison against flush mounting.

Common Pitch Errors and Misreadings

Three common errors occur when measuring or specifying pitch. First, confusing the format: a 6/12 pitch (26.57 degrees, 50 percent slope) is six inches of rise per twelve inches of run, not six degrees and not six percent. The format is rise-over-run, not angle. Second, measuring on the underlayment instead of the rafter: underlayment dips slightly between rafters and over-rounds at the ridge, introducing measurement error. Third, taking a single measurement on a multi-pitch roof: each plane needs its own measurement, and the main roof pitch is not the same as the porch pitch or the dormer pitch.

Pitch and Architectural Style

Different architectural styles have characteristic pitch ranges. Ranch-style homes typically use 3/12 to 5/12 for the low, horizontal aesthetic. Cape Cod homes use 9/12 to 12/12 for the steep, attic-friendly profile. Colonial homes use 8/12 to 10/12. Victorian homes use 10/12 and steeper, with turret elements reaching 18/12 to 24/12. Mediterranean and Spanish Revival homes use 3/12 to 5/12 to suit tile roofing. Modern-contemporary uses anywhere from flat (1/4 in 12) to steep angular forms (8/12 to 12/12). The pitch and shape together define the roof type at gable roof, hip roof, gambrel roof, and mansard roof articles.