11/12 Roof Pitch

A 11/12 roof rises 11 inches for every 12 inches of horizontal run: 42.51°, a 91.7% slope, and 35.7% more surface than its footprint.

11/12 pitch at a glance
Measure	11/12 value
Angle	42.51°
Slope percent	91.7%
Rise per foot of run	11 in
Pitch multiplier (area factor)	1.3566
Hip/valley factor	1.6853
Common rafter length per foot of run	16-1/4"
Plumb cut / seat cut	42.5° / 47.5°

Where you see a 11/12 roof

Typical uses: Tudor and Victorian homes, steep gables and dormers. An 11/12 roof (42.5 degrees) is just shy of 45. It is uncommon on main roofs but shows up on decorative gables and dormers. Material quantities climb fast: the roof has about 36% more surface than its footprint.

Roof area at 11/12

11/12 formulas

Angle = arctan(11 ÷ 12) = 42.51° Multiplier = √(11² + 12²) ÷ 12 = 1.3566 Roof area = footprint × 1.3566 Rafter = run × 1.3566 Ridge height = run × 11 ÷ 12

Worked examples

Roof area. A 48 × 30 ft house with 1 ft overhangs has a 50 × 32 = 1,600 sq ft footprint. At 11/12: 1,600 × 1.3566 = 2,171 sq ft, or 21.7 squares before waste.

Rafter. A 28 ft span with a 1-1/2" ridge board has a 13.938 ft run. Line length = 13.938 × 1.3566 = 18' 10-7/8"; add an 18" overhang (2' 7/16" along the slope) for 20' 11-5/16". The ridge sits 12' 10" above the plate line. Try other spans in the rafter calculator.

11/12 rafter lengths and ridge heights

Common rafters at 11/12, measured to the center of the ridge
Building span	Run	Rafter (no overhang)	Ridge rise
16 ft	8 ft	10' 10-1/4"	7' 4"
20 ft	10 ft	13' 6-13/16"	9' 2"
24 ft	12 ft	16' 3-3/8"	11' 0"
28 ft	14 ft	18' 11-7/8"	12' 10"
32 ft	16 ft	21' 8-7/16"	14' 8"
36 ft	18 ft	24' 5"	16' 6"

Roof area by footprint at 11/12

Footprint to roof area at 11/12
Footprint (incl. overhang)	Roof area	Squares
1,000 sq ft	1,357 sq ft	13.6
1,500 sq ft	2,035 sq ft	20.3
2,000 sq ft	2,713 sq ft	27.1
2,500 sq ft	3,391 sq ft	33.9
3,000 sq ft	4,070 sq ft	40.7

Materials and walkability

Shingles: Yes. 4/12 and steeper takes a standard shingle installation.
Walkable? Not without equipment. Plan on roof jacks, harnesses and anchors.

← 10/12 pitch · 12/12 pitch → · All pitches in degrees

Frequently asked questions

How many degrees is a 11/12 roof pitch?

A 11/12 roof pitch is 42.51 degrees.

What is the multiplier for a 11/12 pitch?

The pitch multiplier for 11/12 is 1.3566. Multiply the footprint area or horizontal run by it to get the sloped area or rafter length.

Can you put shingles on a 11/12 roof?

Yes. 4/12 and steeper takes a standard shingle installation.

Is a 11/12 roof walkable?

Not without equipment. Plan on roof jacks, harnesses and anchors.

Last reviewed 2026-10-10. Results are estimates for planning; confirm quantities with your supplier and requirements with your local building code and the manufacturer's instructions.