Roof Pitch to Angle Conversion Table

Pitch is written as rise over a run of 12. Everything else in this table is that ratio expressed differently: the angle is its arctangent, the slope factor is the hypotenuse per unit of run, and the grade is the ratio as a percentage.

Pitch	Angle	Slope factor	Grade
1/12	4.76°	× 1.0035	8.3%
2/12	9.46°	× 1.0138	16.7%
3/12	14.04°	× 1.0308	25.0%
4/12	18.43°	× 1.0541	33.3%
5/12	22.62°	× 1.0833	41.7%
6/12	26.57°	× 1.1180	50.0%
7/12	30.26°	× 1.1577	58.3%
8/12	33.69°	× 1.2019	66.7%
9/12	36.87°	× 1.2500	75.0%
10/12	39.81°	× 1.3017	83.3%
11/12	42.51°	× 1.3566	91.7%
12/12	45.00°	× 1.4142	100.0%
13/12	47.29°	× 1.4743	108.3%
14/12	49.40°	× 1.5366	116.7%
15/12	51.34°	× 1.6008	125.0%
16/12	53.13°	× 1.6667	133.3%
17/12	54.78°	× 1.7341	141.7%
18/12	56.31°	× 1.8028	150.0%

Using the slope factor

The slope factor is the column that earns its keep. Multiply any horizontal measurement by it and you get the sloped one:

Roof area. 1,000 sq ft of footprint under a 6/12 roof is 1,118 sq ft of actual roof surface. Order shingles against that number, not the footprint.
Rafter length. A level run of 143¼″ on a 6/12 gives a rafter line length of just over 160″.
Overhang. A level 12″ overhang needs 13⁷⁄₁₆″ of rafter tail on a 6/12.

The pitches worth knowing by heart

4/12 is about the shallowest most shingle manufacturers will warrant without extra underlayment. 6/12 is the workhorse residential pitch. 12/12 is exactly 45 degrees, which makes it a useful reference point: if the angle is over 45, the rise is greater than the run.

Somewhere around 7/12 is where most people stop walking a roof comfortably, which is a scheduling and staging fact as much as a geometric one.

Common questions

What angle is a 6/12 roof pitch?

26.57 degrees. Pitch converts to an angle by taking the arctangent of the rise over the run, so 4/12 is 18.43 degrees, 6/12 is 26.57, 8/12 is 33.69, and 12/12 is exactly 45 degrees.

What is a roof slope factor used for?

Multiplying a horizontal measurement to get the sloped one. It converts a flat footprint area into actual roof area for ordering material, and it converts a level run into rafter length. A 6/12 roof has a slope factor of 1.1180, so 1,000 square feet of footprint is 1,118 square feet of roof.

What is the difference between roof pitch, slope and grade?

Pitch here means rise over a run of 12, written as 6/12. Slope is the same relationship expressed as an angle in degrees. Grade is that ratio as a percentage, so a 6/12 roof is a 50 percent grade. All three describe the same roof.

Check it against the job. Building codes, span tables and product specifications vary by jurisdiction and manufacturer. Your approved drawings and your local code govern, not this page.