4/12 Pitch in Degrees: Angle, Slope & What It Means for Your Roof (2026)

A 4/12 pitch is 18.43 degrees, or a 33.3% slope: the roof rises 4 inches for every 12 inches of horizontal run. It is one of the most common pitches on single-story homes and ranch-style houses across Waukegan and Lake County, Illinois, because it sheds water well while staying easy to walk on and easy to roof. If you are checking a bid, measuring for shingles, or just trying to make sense of a contractor’s note that says “4/12”, this guide gives you the exact angle, the slope math, and what this pitch means for materials, walkability, and snow. To convert any pitch — or to work out your own roof’s numbers from measurements — use our roof pitch calculator, which turns rise and run into degrees in seconds.

How the Math Works

Pitch notation is rise over run. The first number is how many inches the roof rises; the second is always 12 inches of run. The angle comes from the arctangent: degrees = atan(rise / 12). For a 4/12 pitch, atan(4 / 12) = atan(0.333) = 18.43 degrees. The slope percentage is simpler: (4 / 12) x 100 = 33.3%. Over a 12-foot horizontal run, a 4/12 roof rises 4 feet. That rise matters for ordering: the roof surface is larger than the footprint. The area multiplier for a 4/12 pitch is 1.054, so a 1,000 square foot footprint carries about 1,054 square feet of roof surface before hips, valleys, and overhangs are counted. Measure the run from the outside of the wall to the ridge, not along the slope, or the math will overstate the rise.

Pitch-to-Degrees Reference Table

Every common residential pitch, with the angle and slope for each. Your pitch is shown in bold.

Pitch	Angle	Slope	Category
2/12	9.46 degrees	16.7%	Low
3/12	14.04 degrees	25.0%	Low
4/12	18.43 degrees	33.3%	Low-moderate
5/12	22.62 degrees	41.7%	Moderate
6/12	26.57 degrees	50.0%	Moderate
8/12	33.69 degrees	66.7%	Steep
9/12	36.87 degrees	75.0%	Steep
10/12	39.81 degrees	83.3%	Very steep
12/12	45.00 degrees	100.0%	Very steep

What This Pitch Looks Like

A 4/12 roof looks like a gentle, friendly slope — clearly pitched, but nowhere near steep. From the street it reads as a classic suburban roofline, lower and wider than a 6/12 or 8/12 gable. Inside, a 4/12 pitch leaves limited but usable attic space: enough for storage and ductwork in most homes, though rarely enough for a finished room without dormers. Because the slope is moderate, gutters and eaves do most of the water-shedding work, and the roofline stays low enough that wind loads are modest compared with steep gables.

Can You Walk on It?

Yes, for most roofers a 4/12 pitch is walkable. It is at the comfortable end of walkable pitches: crews work on it in standard roofing shoes without staging or roof jacks in dry conditions, and homeowners can walk it carefully for a visual check or gutter cleaning. That walkability is one reason 4/12 roofs are cheaper to service — no steep-roof labor premium, no harness-and-rope setup for routine work. Wet, icy, or moss-covered surfaces change the equation completely: a damp 4/12 can be as treacherous as a steeper dry roof, so never walk any roof in rain or frost. In winter, Lake County ice makes even a gentle pitch dangerous underfoot.

Materials That Suit This Pitch

Almost every common roofing material suits a 4/12 pitch, which is another reason it is so popular. Architectural asphalt shingles are the default here and install to standard manufacturer specs at this pitch, with no special low-slope underlayment required. Standing seam metal also performs beautifully, shedding water fast and handling snow well. Clay and concrete tile work too, though tile’s weight means the structure must be checked. What does not suit a 4/12 pitch is a flat-roof membrane system — those belong on slopes below 2/12. At 4/12, choose on looks, budget, and lifespan rather than on pitch limits, because the pitch itself rules almost nothing out.

Illinois Snow, Ice and Wind Notes

In Lake County winters, a 4/12 pitch is a good compromise. It is steep enough that snow usually slides or melts off before building into a deep, heavy load, but shallow enough that snow does not avalanche off in dangerous sheets the way it can from a very steep metal roof. The main cold-weather watch item is ice dams: on a moderate pitch, meltwater can refreeze at the eaves, back up under shingles, and leak. Proper attic insulation, ventilation, and an ice-and-water shield along the eaves — standard practice on a professional install — handle that risk. If your home has a history of ice dams, tell your roofer before the bid, not after the first leak.

How to Measure Your Own Pitch

You can measure a 4/12 pitch with a 12-inch level and a tape measure. Hold the level horizontally against the roof surface or a rafter, measure 12 inches out from the contact point, then measure straight down from the level to the roof at that 12-inch mark. A 4-inch drop means a 4/12 pitch, or 18.43 degrees. From inside the attic, measure the same way along a rafter. From the ground, a phone inclinometer app aimed along the slope gives a rough reading, but verify before ordering materials. For exact numbers on your own roof, run the measurements through our roof pitch calculator. For the neighboring pitches, see our guides to 5/12 pitch in degrees and 3/12 pitch in degrees. Every calculator on the site lives in the roofing calculators hub.

Common Mistakes With This Pitch

The most common mistake with a 4/12 pitch is treating it like a flat roof. It is not: water still needs proper flashing at valleys, chimneys, and walls, and gutters still need a fall toward the downspouts. A second mistake is measuring the slope instead of the run — running the tape along the roof surface instead of horizontally inflates the rise and can push a true 4/12 reading up to 5/12 or higher, which throws off material orders. A third mistake is skipping the ice-and-water shield at the eaves because the pitch “looks gentle enough.” On a Lake County roof, the eaves are exactly where ice dams form, and the shield is cheap insurance against the most common winter leak. Finally, do not assume a 4/12 attic is a room: headroom at the eaves is minimal, and finishing it without dormers or a structural check creates a cramped, non-compliant space.

Frequently Asked Questions

What degrees is a 4/12 pitch?

A 4/12 pitch is 18.43 degrees. The roof rises 4 inches for every 12 inches of horizontal run, and atan(4 / 12) = 18.43 degrees. Its slope is 33.3%.

What angle is a 4/12 pitch?

The angle of a 4/12 pitch is 18.43 degrees — the same figure, phrased differently. “Angle” and “degrees” describe the same measurement: the tilt of the roof surface above horizontal, worked out as atan(rise / 12).

Is a 4/12 pitch roof walkable?

Yes, in dry conditions a 4/12 pitch is walkable for roofers and careful homeowners. It is one of the easiest pitches to work on, which keeps service costs down. Never walk a roof when it is wet, icy, or moss-covered — a damp 4/12 can be as slippery as a much steeper dry roof.

What roofing materials work on a 4/12 pitch?

Almost all of them: architectural asphalt shingles (the default), standing seam metal, and clay or concrete tile all suit a 4/12 pitch. Standard shingle installation applies, with no special low-slope underlayment needed. Flat-roof membranes are the exception — they belong on slopes below 2/12.

How do you measure a 4/12 pitch?

Hold a 12-inch level horizontally against the roof or a rafter, measure 12 inches out, then measure straight down to the roof at that mark. A 4-inch drop means a 4/12 pitch, or 18.43 degrees. Verify with the roof pitch calculator before ordering materials.