What is a 6/12 roof pitch in degrees?

A 6/12 roof is 26.57°, or a 50% slope. Its rafter multiplier is 1.1180, so each foot of run takes 13.42 inches of rafter.

What is the minimum roof pitch for asphalt shingles?

IRC R905.2.2 allows asphalt shingles down to 2/12. Between 2/12 and 4/12, double underlayment is required. Below 2/12, use a low-slope system such as modified bitumen or standing-seam metal.

How do I find my roof pitch without getting on the roof?

Measure from the attic: put a level against a rafter, mark 12 inches, and measure straight up to the rafter. You can also measure the gable from the ground with a laser or read the pitch off the house plans.

What is the difference between pitch and slope?

In everyday use they mean the same thing, rise over run, written as x/12. Slope can also be written as a percentage (6/12 = 50%). Some older texts define pitch as rise over the full span, which makes a 6/12 roof a 1/4 pitch.

How many squares of roofing do I need?

Multiply the footprint area, including overhangs, by the rafter multiplier for your pitch, then divide by 100. A 1,800 sq ft footprint at 7/12 is about 20.84 squares before waste.

What does the hip and valley multiplier mean?

It is the length of a hip or valley rafter for each unit of common rafter run on a regular hip roof, where both sides have the same pitch. At 6/12 it is 1.5, so a hip over 10 feet of common run is 15 feet long before cuts.

Roof Pitch Calculator

Enter rise and run, a pitch, or an angle. Get the pitch in x/12, the angle in degrees, the rafter and hip multipliers, the roof area in squares, and which roofing materials the code allows at that slope.

By ChiselJobs Team · Updated October 12, 2026

Measurements

I know the

RiseRun (same unit)

Measure rise and run in the same unit. A common field method: hold a level 12 inches long against the rafter and measure straight up to the underside of the roof.

Footprint area incl. overhangs (sq ft, optional)

Roof Pitch

Pitch

6/12

26.57° · 50% slope

Rafter Multiplier

1.118

Hip / Valley Multiplier

1.5

Common Rafter per Ft of Run

13.42 in

Hip / Valley per Ft of Run

18 in

Roofing Allowed at This Pitch

Standing-seam metal panelsmin 0.25/12 · IRC R905.10.2
Built-up roofingmin 0.25/12 · IRC R905.9.1
Modified bitumenmin 0.25/12 · IRC R905.11.1
Lapped metal panels, with sealantmin 0.5/12 · IRC R905.10.2
Mineral-surfaced roll roofingmin 1/12 · IRC R905.5.2
Asphalt shinglesmin 2/12 · IRC R905.2.2
Clay and concrete tilemin 2.5/12 · IRC R905.3.2
Metal roof shinglesmin 3/12 · IRC R905.4.2
Lapped metal panels, no sealantmin 3/12 · IRC R905.10.2
Wood shinglesmin 3/12 · IRC R905.7.2
Wood shakesmin 3/12 · IRC R905.8.2
Slate shinglesmin 4/12 · IRC R905.6.2

What Is Roof Pitch?

Roof pitch is how many inches a roof rises for every 12 inches it runs horizontally. A 6/12 roof (said "six in twelve") climbs 6 inches over each foot of run. Carpenters work in x/12 because it maps straight onto a framing square: the 12 is the body of the square and the rise is the tongue.

The same steepness can be written three ways. Pitch is 6/12. Slope as a percentage is rise divided by run, so 6/12 is 50%. The angle is about 26.57°. Older carpentry books also use "pitch" for rise divided by the full span, which makes a 6/12 roof a "1/4 pitch" roof, so check which meaning a set of plans uses.

How to Measure Roof Pitch

There are four common ways, from easiest to most accurate.

From the attic: hold a level against the bottom of a rafter, mark 12 inches along the level, and measure straight up from that mark to the underside of the rafter. That number is the rise.
From the roof surface: set a level on the shingles, level it, and measure from the 12-inch mark down to the roof. Shingle thickness adds a little error.
From the gable end: measure the total rise from the top plate to the ridge and half the building width, then enter them as rise and run.
From the plans: the pitch is usually drawn as a small triangle on the elevations or listed in the framing notes.

Roof Pitch Formulas

Everything comes from the right triangle formed by the rise, the run and the rafter. Rise and run just need to be in the same unit.

Pitch

Pitch = rise ÷ run × 12

Angle

Angle = arctan(pitch ÷ 12)

Slope percent

Slope % = pitch ÷ 12 × 100

Rafter multiplier

M = √(pitch² + 144) ÷ 12

Hip and valley multiplier

H = √(pitch² + 288) ÷ 12

Roof area

Area = footprint × M

pitch: Rise in inches per 12 inches of run
M: Common rafter length per unit of run
H: Hip or valley rafter length per unit of common run (regular hip)
288: 16.97², the diagonal run of a hip per foot of common run
footprint: Plan area including overhangs, in sq ft

One roofing square is 100 sq ft of roof surface. The area formula assumes every roof plane has the same pitch.

Worked Example: Pitch From a Measurement

From the attic, you measure 4 inches of rise over 10 inches of run.

Pitch: 4 ÷ 10 × 12 = 4.8/12.
Angle: arctan(4 ÷ 10) = 21.80°.
Slope: 4.8 ÷ 12 = 40.0%.

Result: about 4.8/12, or 21.80°. That is above the 4/12 line, so asphalt shingles need only a single layer of underlayment.

Worked Example: Roofing Squares for a 7/12 Roof

A house has a 1,800 sq ft footprint including overhangs and a 7/12 roof on every plane. How much roofing is needed?

Rafter multiplier: √(7² + 144) ÷ 12 = √193 ÷ 12 = 1.1577.
Roof area: 1,800 × 1.1577 = 2,084 sq ft.
Squares: 2,084 ÷ 100 = 20.84 squares.

Result: about 20.84 squares before waste. Add more for hips, valleys and starter courses.

Roof Pitch to Degrees Chart

Common pitches with their angle, slope, and rafter and hip multipliers.

Calculated from the formulas above. Multipliers match the rafter table on a steel framing square.
Pitch	Angle	Slope	Rafter ×	Hip / valley ×
1/12	4.76°	8.3%	1.0035	1.4167
2/12	9.46°	16.7%	1.0138	1.4240
3/12	14.04°	25.0%	1.0308	1.4361
4/12	18.43°	33.3%	1.0541	1.4530
5/12	22.62°	41.7%	1.0833	1.4743
6/12	26.57°	50.0%	1.1180	1.5000
7/12	30.26°	58.3%	1.1577	1.5298
8/12	33.69°	66.7%	1.2019	1.5635
9/12	36.87°	75.0%	1.2500	1.6008
10/12	39.81°	83.3%	1.3017	1.6415
11/12	42.51°	91.7%	1.3566	1.6853
12/12	45.00°	100.0%	1.4142	1.7321
14/12	49.40°	116.7%	1.5366	1.8333
16/12	53.13°	133.3%	1.6667	1.9437
18/12	56.31°	150.0%	1.8028	2.0616
24/12	63.43°	200.0%	2.2361	2.4495

Minimum Roof Pitch by Roofing Material

The International Residential Code sets a minimum slope for each roof covering. Manufacturer instructions can require more.

Source: International Residential Code, Section R905. Local amendments may differ.
Roof covering	Minimum pitch	IRC section	Note
Standing-seam metal panels	0.25/12	R905.10.2
Built-up roofing	0.25/12	R905.9.1
Modified bitumen	0.25/12	R905.11.1
Lapped metal panels, with sealant	0.5/12	R905.10.2
Mineral-surfaced roll roofing	1/12	R905.5.2
Asphalt shingles	2/12	R905.2.2	Double underlayment below 4/12
Clay and concrete tile	2.5/12	R905.3.2	Double underlayment below 4/12
Metal roof shingles	3/12	R905.4.2
Lapped metal panels, no sealant	3/12	R905.10.2
Wood shingles	3/12	R905.7.2
Wood shakes	3/12	R905.8.2
Slate shingles	4/12	R905.6.2

Low-Slope, Conventional and Steep Roofs

OSHA defines a low-slope roof as 4/12 or less and a steep roof as anything above 4/12 (29 CFR 1926.500). Most houses in North America land between 4/12 and 9/12, which sheds water and snow well and is still workable from the roof surface with care.

Steeper roofs give more attic space and a traditional look but take more material, need roof jacks or staging to work on, and cost more labor per square. Below 4/12, the code limits which coverings you can use and often requires extra underlayment, as the table above shows.