12/12 Roof Pitch

A 12/12 pitch rises 12 inches for every 12 inches of run: 45.00°, a 100.0% slope and a multiplier of 1.414.

Angle45.00°
Percent slope100.0%
Multiplier1.4142
Rafter per ft run16.97 in

Roof pitch

12/12 pitch

45.0° · 100.0% · ×1.414

12/12 is 45.00°, a 100.0% slope, and the roof is 41.4% larger than its footprint.

Angle45.00°
Percent slope100.0%
Pitch multiplier1.4142
Hip and valley factor1.7321
Rafter per foot of run16.97 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 12/12 pitch looks like

At 12/12 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 12 inches for every 12 inches of run. That is a 45.00° angle, a 100.0% slope and a roof surface 41.4% larger than its footprint.

Roof area at 12/12

Multiply the footprint by 1.4142. For common footprints, with no overhang and 10% extra on the shingles:

Roof area and shingles at 12/12
Footprint	Roof area	Squares	Bundles with 10% extra
1,000 sq ft	1,414 sq ft	14.1	47
1,500 sq ft	2,121 sq ft	21.2	71
2,000 sq ft	2,828 sq ft	28.3	94
2,500 sq ft	3,536 sq ft	35.4	117
3,000 sq ft	4,243 sq ft	42.4	141

Rafter length at 12/12

Each foot of run adds 16.97 inches of common rafter, or 1.7321 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 12/12
Run	Rise	Rafter length
4 ft	4 ft 0 in	5 ft 7⅞ in
6 ft	6 ft 0 in	8 ft 5⅞ in
8 ft	8 ft 0 in	11 ft 3¾ in
10 ft	10 ft 0 in	14 ft 1¾ in
12 ft	12 ft 0 in	16 ft 11⅝ in
14 ft	14 ft 0 in	19 ft 9⅝ in
16 ft	16 ft 0 in	22 ft 7½ in

Roofing materials at 12/12

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 12/12 roof?

OSHA classes any roof over 4 in 12 as steep. At 12/12 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 12/12 roof pitch?

45.00 degrees, a 100.0% slope.

What is the multiplier for a 12/12 roof?

1.4142. Multiply the footprint area by it to get roof area. The hip/valley factor is 1.7321.

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

41.4% over the footprint. A 2,000 sq ft footprint becomes 2,828 sq ft of roof, 28.3 squares.

Is 12/12 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 12/12 roof rise over a 12-foot run?

12 feet. Over a 12-foot run the roof climbs 12 feet, which is 16 ft 11⅝ 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)