A roof pitch such as 6:12 means the roof rises 6 inches for every 12 inches it runs horizontally. That same slope can also be written as 26.57 degrees or as a 50 percent grade, and each format is used by different trades: roofers order by pitch, architects draw in degrees, and drainage or ramp work is usually quoted in percent. The chart in this article converts every standard pitch from 1:12 to 12:12 into degrees, percent and rafter length per foot of run, so you can translate between the three without doing trigonometry. Most American houses sit between 4:12 and 6:12, which is 18.43 to 26.57 degrees.
Pitch is always rise over run, and the run is conventionally fixed at 12 because American framing lumber and tape measures work in feet and inches. If you do not know your pitch yet, measure it from the attic, from a gable end, or safely from the ground with a level and tape; our step-by-step guide on how to measure roof pitch walks through all three methods. Once you have a rise and a run in any units, the conversions below apply, because pitch is a ratio: a roof that rises 3 feet over a 6-foot run is the same slope as 6:12.
The full roof pitch chart: 1:12 to 12:12
The chart below covers the full standard range. The rafter length column is the length of sloping rafter needed to cover 12 inches of horizontal run, before you add anything for the ridge, the eaves overhang or the thickness of the ridge board. Read it as: pitch, angle in degrees, slope percent, rafter length per 12 inches of run. 1:12 — 4.76° — 8.33% — rafter 12.04 in; 2:12 — 9.46° — 16.67% — rafter 12.17 in; 3:12 — 14.04° — 25% — rafter 12.37 in; 4:12 — 18.43° — 33.33% — rafter 12.65 in; 5:12 — 22.62° — 41.67% — rafter 13.00 in; 6:12 — 26.57° — 50% — rafter 13.42 in.
Continuing the chart into the steep range: 7:12 — 30.26° — 58.33% — rafter 13.89 in; 8:12 — 33.69° — 66.67% — rafter 14.42 in; 9:12 — 36.87° — 75% — rafter 15.00 in; 10:12 — 39.81° — 83.33% — rafter 15.62 in; 11:12 — 42.51° — 91.67% — rafter 16.28 in; 12:12 — 45° — 100% — rafter 16.97 in. Notice that 12:12 is exactly 45 degrees and exactly 100 percent, which is a handy anchor: percent and degrees only coincide at that one point, and everywhere else they are different numbers describing the same slope. A 100 percent slope sounds extreme until you realize it is simply a 45-degree angle.
How pitch converts to degrees, percent and rafter length
Each column comes from a short formula. Angle in degrees is arctan(rise ÷ 12) — for 6:12 that is arctan(0.5) = 26.57°. Slope percent is rise ÷ 12 × 100, so 6 ÷ 12 × 100 = 50%. Rafter length is the hypotenuse of the framing triangle, √(12² + rise²): for 6:12, √(144 + 36) = √180 = 13.42 inches. If your rise and run are not in a neat per-12 form, divide both by the run and multiply by 12 first, or let the roof pitch calculator do the conversion from any rise and run, including feet and meters.
Pitch, slope and grade: three words for the same steepness
Three words describe this same slope and get swapped loosely, so fix them now. Pitch is the framing term: rise over a 12-inch run, written 6:12. Slope is the general term for any inclined surface, expressed as a ratio, a percent or an angle depending on the trade. Grade is the civil-works term, almost always a percent, used for roads, ramps and drainage — a 6:12 roof would be a 50 percent grade, a number that belongs on no road. When a supplier, inspector or plan uses one of these words, check which format the number is in before comparing it with the chart; most pitch confusion is two people using different words for identical steepness.
Which roofing materials suit each pitch
As a general rule of thumb — always subject to the manufacturer's written minimums and your local code — very low pitches under about 2:12 belong to membrane and low-slope systems such as EPDM rubber, TPO, modified bitumen or built-up roofing, because water moves too slowly for lapped shingles to shed it reliably. Asphalt shingles, the most common US roofing, are commonly approved from 2:12 upward only with doubled underlayment or an ice-and-water membrane over the whole deck, and are installed in the standard way from 4:12 up. Between those ranges the details matter more than the headline pitch, so read the shingle wrapper before you assume.
Metal roofing splits by seam type: hidden-fastener standing seam panels are often rated for lower pitches than exposed-fastener corrugated panels, because every exposed screw hole is a potential leak path on a slow-draining roof, so check the specific panel's minimum rather than a generic number. Clay and concrete tile are usually installed at 4:12 or steeper and are far heavier than shingles, which means an older house may need a structural check before a tile conversion even if the pitch is fine. Slate and wood shakes have their own minimums and exposure rules for the same reason: pitch, material and installation method always work as a package.
Underlayment is the quiet variable in the low-pitch ranges. Between 2:12 and 4:12, shingle manufacturers commonly require either two layers of underlayment or a full-coverage ice-and-water membrane, because wind-driven rain and slow runoff can push water up under laps that shed perfectly well at steeper pitches. In snow country, an ice-and-water membrane at the eaves is often required by code or warranty regardless of pitch, extending up the roof to at least 24 inches inside the exterior wall line. None of this changes how you read the chart — but a 3:12 roof is a system of shingles plus membrane, priced and warranted as such, not a cheaper version of a 6:12 roof.
The pitches most houses actually use
Drive through most US suburbs and you will see 4:12 to 6:12 over and over. That band drains rain well, keeps shingle warranties straightforward, leaves usable attic volume, and stays affordable to frame and to re-roof. Low 3:12 pitches show up on ranch houses and modern low-profile designs, where the roof is a quiet background element. At the other end, 8:12 to 12:12 appears on Cape Cods, cabins, A-frames and snow-country builds where shedding load matters and the steep roof is part of the look. Additions usually copy the existing house pitch so the rooflines meet cleanly, which is why measuring what you already have is the first step in most projects.
Snow shedding versus walking on the roof
Steeper roofs shed snow and debris instead of holding them, which reduces ice-dam and standing-load problems in cold climates; the same math that governs ramps and driveways applies here, and the plain slope calculator shows how percent grade and angle diverge as slopes grow. The trade-off is access: a 4:12 roof can usually be walked carefully by a professional, a 6:12 is noticeably less comfortable, and anything steeper generally needs roof jacks, harnesses or staging for safe work. Never treat walkability as a DIY invitation — pitch, surface, weather and footwear all change the risk, and any doubt means working from the ground or hiring out.
Scaling the chart to a real roof
To scale the rafter column to a real roof, multiply the per-12 rafter length by your horizontal run in feet and divide by 12 — or, easier, treat the chart value as inches of rafter per foot of run. Example: a house 28 feet wide with a centered ridge has a 14-foot horizontal run on each side. At 6:12 the rafter factor is 13.42 inches per foot of run, so each rafter is 14 × 13.42 = 187.9 inches, about 15 feet 8 inches, before adding the eaves overhang and accounting for the ridge board. That is the number a framer or truss designer starts from, and it is why a small pitch change early in a design is cheap while the same change after framing is not.
Simple gable roofs are what the chart models best. Hip roofs use the same common-rafter pitch on every slope, but hip rafters run at 45 degrees in plan view and are longer than commons at the same pitch, which is why hip rafter lengths come from their own tables. Valleys concentrate water from two slopes into one channel, so valley metal or woven shingles carry extra detailing and their own minimum-pitch cautions from manufacturers. Dormers often run a lower pitch than the main roof for headroom, which can drop a dormer into membrane territory even on a steep house. For anything beyond a single-slope or simple gable roof, treat the chart as the starting figure and let a framer or truss designer price the actual geometry.
Common roof pitch mistakes
The most common chart mistake is mixing up percent and degrees: a 50 percent slope is 26.57 degrees, not 50 degrees, and quoting one as the other doubles the apparent steepness. Second is measuring pitch over the roofing surface, where shingle butt edges and texture throw the level off; measure against the rafter or the deck instead. Third is using the full building span as the run rather than the half-span each rafter actually covers. Fourth is forgetting that chart rafter lengths exclude overhangs, so a material order built straight from the chart comes up short at the eaves. Finally, a chart is a conversion tool, not an approval: manufacturer minimums and local code always outrank any general table.
If you are planning a new build, porch or addition, pick the pitch with three things in view: the covering you want and its minimum pitch, the look of similar houses nearby (and any HOA or historic-district rules), and how snow and heavy rain behave in your climate. Matching an existing roofline usually wins for additions. When the plan is set, run your exact rise and run through the roof pitch calculator to get the pitch, angle, percent and rafter length for your numbers rather than the nearest row of the chart, and keep the chart above as the quick cross-check it is meant to be.