1/12 Roof Pitch

A 1/12 pitch rises 1 inches for every 12 inches of run: 4.76°, a 8.3% slope and a multiplier of 1.003.

Angle4.76°
Percent slope8.3%
Multiplier1.0035
Rafter per ft run12.04 in

Roof pitch

1/12 pitch

4.8° · 8.3% · ×1.003

1/12 is 4.76°, a 8.3% slope, and the roof is 0.3% larger than its footprint.

Angle4.76°
Percent slope8.3%
Pitch multiplier1.0035
Hip and valley factor1.4167
Rafter per foot of run12.04 in
Slope class (OSHA)Low slope (4 in 12 or less)

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 1/12 pitch looks like

At 1/12 the roof is nearly flat. It sheds water slowly, so material choice matters more than it does on a steeper roof. The roof rises 1 inches for every 12 inches of run. That is a 4.76° angle, a 8.3% slope and a roof surface 0.3% larger than its footprint.

Roof area at 1/12

Multiply the footprint by 1.0035. For common footprints, with no overhang and 10% extra on the shingles:

Roof area and shingles at 1/12
Footprint	Roof area	Squares	Bundles with 10% extra
1,000 sq ft	1,003 sq ft	10.0	34
1,500 sq ft	1,505 sq ft	15.1	50
2,000 sq ft	2,007 sq ft	20.1	67
2,500 sq ft	2,509 sq ft	25.1	83
3,000 sq ft	3,010 sq ft	30.1	100

Rafter length at 1/12

Each foot of run adds 12.04 inches of common rafter, or 1.4167 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 1/12
Run	Rise	Rafter length
4 ft	0 ft 4 in	4 ft 0⅛ in
6 ft	0 ft 6 in	6 ft 0¼ in
8 ft	0 ft 8 in	8 ft 0⅜ in
10 ft	0 ft 10 in	10 ft 0⅜ in
12 ft	1 ft 0 in	12 ft 0½ in
14 ft	1 ft 2 in	14 ft 0⅝ in
16 ft	1 ft 4 in	16 ft 0⅝ in

Roofing materials at 1/12

GAF gives 2:12 as the absolute minimum slope for asphalt shingles, so this pitch needs a low-slope roofing system rather than ordinary shingles. Some metal panels allow very low slopes: MBCI lists ½:12 for its PBR panel. Ask a roofer which system fits, and follow your product data sheet.

Can you walk a 1/12 roof?

OSHA's fall-protection rules class a roof of 4 in 12 or less as low slope, and 1/12 meets that definition. Low slope does not mean safe: wet, dusty or leaf-covered roofs are slippery, and falls from any height hurt. This is general information, not safety advice.

Frequently asked questions

What angle is a 1/12 roof pitch?

4.76 degrees, a 8.3% slope.

What is the multiplier for a 1/12 roof?

1.0035. Multiply the footprint area by it to get roof area. The hip/valley factor is 1.4167.

How much roof area does a 1/12 pitch add?

0.3% over the footprint. A 2,000 sq ft footprint becomes 2,007 sq ft of roof, 20.1 squares.

Is 1/12 a low-slope roof?

By OSHA’s definition, yes: 4 in 12 or less is low slope. GAF adds rules below 4:12, including double underlayment from 2:12 to 4:12, and gives 2:12 as the absolute minimum slope for shingles.

How much does a 1/12 roof rise over a 12-foot run?

1 feet. Over a 12-foot run the roof climbs 1 feet, which is 12 ft 0½ 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)