11/12 Roof Pitch

A 11/12 pitch rises 11 inches for every 12 inches of run: 42.51°, a 91.7% slope and a multiplier of 1.357.

Angle42.51°
Percent slope91.7%
Multiplier1.3566
Rafter per ft run16.28 in

Roof pitch

11/12 pitch

42.5° · 91.7% · ×1.357

11/12 is 42.51°, a 91.7% slope, and the roof is 35.7% larger than its footprint.

Angle42.51°
Percent slope91.7%
Pitch multiplier1.3566
Hip and valley factor1.6853
Rafter per foot of run16.28 in
Slope class (OSHA)Steep (over 4 in 12)

Pitch is rise in inches over 12 inches of run. The multiplier turns a flat measurement into sloped length: multiply the footprint area by it to get roof area.

Planning estimate, not a quote. Disclaimer

What a 11/12 pitch looks like

At 11/12 the roof is very steep, steeper than the range GAF says covers most US homes. Expect more surface area, careful staging and more attention to safety. The roof rises 11 inches for every 12 inches of run. That is a 42.51° angle, a 91.7% slope and a roof surface 35.7% larger than its footprint.

Roof area at 11/12

Multiply the footprint by 1.3566. For common footprints, with no overhang and 10% extra on the shingles:

Roof area and shingles at 11/12
Footprint	Roof area	Squares	Bundles with 10% extra
1,000 sq ft	1,357 sq ft	13.6	45
1,500 sq ft	2,035 sq ft	20.3	68
2,000 sq ft	2,713 sq ft	27.1	90
2,500 sq ft	3,391 sq ft	33.9	112
3,000 sq ft	4,070 sq ft	40.7	135

Rafter length at 11/12

Each foot of run adds 16.28 inches of common rafter, or 1.6853 ft of hip or valley rafter per foot of common run. For some typical runs, measured to the ridge centerline:

Rise and common rafter length at 11/12
Run	Rise	Rafter length
4 ft	3 ft 8 in	5 ft 5⅛ in
6 ft	5 ft 6 in	8 ft 1⅝ in
8 ft	7 ft 4 in	10 ft 10¼ in
10 ft	9 ft 2 in	13 ft 6¾ in
12 ft	11 ft 0 in	16 ft 3⅜ in
14 ft	12 ft 10 in	18 ft 11⅞ in
16 ft	14 ft 8 in	21 ft 8½ in

Roofing materials at 11/12

Shingles and metal both work, but check the manufacturer’s instructions for steep-slope fastening and staging. For its TimberSteel metal roofing, GAF notes that a slope over 6:12 may affect walkability because the product can be slippery when wet.

Can you walk a 11/12 roof?

OSHA classes any roof over 4 in 12 as steep. At 11/12 you should not count on simply walking it: GAF notes, for its metal roofing, that slopes over 6:12 may affect walkability. Use fall protection and, if in doubt, hire a roofer. This is general information, not safety advice.

Frequently asked questions

What angle is a 11/12 roof pitch?

42.51 degrees, a 91.7% slope.

What is the multiplier for a 11/12 roof?

1.3566. Multiply the footprint area by it to get roof area. The hip/valley factor is 1.6853.

How much roof area does a 11/12 pitch add?

35.7% over the footprint. A 2,000 sq ft footprint becomes 2,713 sq ft of roof, 27.1 squares.

Is 11/12 a steep roof?

By OSHA’s definition, yes: anything over 4 in 12 is steep for fall-protection rules. GAF puts most US homes between 4:12 and 9:12.

How much does a 11/12 roof rise over a 12-foot run?

11 feet. Over a 12-foot run the roof climbs 11 feet, which is 16 ft 3⅜ in of rafter along the slope.

Other roof pitches

Other roofing calculators

Sources

OSHA 29 CFR 1926.500: definitions of low-slope and steep roofs (checked Nov 12, 2026)
GAF: Minimum slope for shingles (checked Nov 12, 2026)
Swanson Tool: Roof pitch reference (rafter length per foot of run) (checked Nov 12, 2026)