1/12 Roof Pitch

A 1/12 roof rises 1 inch for every 12 inches of horizontal run: 4.76°, a 8.3% slope, and 0.3% more surface than its footprint.

1/12 pitch at a glance
Measure	1/12 value
Angle	4.76°
Slope percent	8.3%
Rise per foot of run	1 in
Pitch multiplier (area factor)	1.0035
Hip/valley factor	1.4167
Common rafter length per foot of run	12-1/16"
Plumb cut / seat cut	4.8° / 85.2°

Where you see a 1/12 roof

Typical uses: carports, patio covers, shed-style additions and commercial-style low-slope roofs. At under 5 degrees, a 1/12 roof looks flat from the street. It still drains, which is the point: a little slope keeps water from ponding. Shingles are not allowed this low, so the usual coverings are single-ply membranes (TPO, EPDM, PVC), modified bitumen, mechanically seamed standing-seam metal, or mineral-surfaced roll roofing, which the IRC allows down to 1/12.

Roof area at 1/12

1/12 formulas

Angle = arctan(1 ÷ 12) = 4.76° Multiplier = √(1² + 12²) ÷ 12 = 1.0035 Roof area = footprint × 1.0035 Rafter = run × 1.0035 Ridge height = run × 1 ÷ 12

Worked examples

Roof area. A 48 × 30 ft house with 1 ft overhangs has a 50 × 32 = 1,600 sq ft footprint. At 1/12: 1,600 × 1.0035 = 1,606 sq ft, or 16.1 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 × 1.0035 = 13' 11-13/16"; add an 18" overhang (1' 6-1/16" along the slope) for 15' 5-7/8". The ridge sits 1' 2" above the plate line. Try other spans in the rafter calculator.

1/12 rafter lengths and ridge heights

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

Roof area by footprint at 1/12

Footprint to roof area at 1/12
Footprint (incl. overhang)	Roof area	Squares
1,000 sq ft	1,003 sq ft	10.0
1,500 sq ft	1,505 sq ft	15.1
2,000 sq ft	2,007 sq ft	20.1
2,500 sq ft	2,509 sq ft	25.1
3,000 sq ft	3,010 sq ft	30.1

Materials and walkability

Shingles: No. Below 2/12, use a membrane, roll roofing or low-slope metal.
Walkable? Generally yes, in dry conditions with proper footwear and fall protection where required.

2/12 pitch → · All pitches in degrees

Frequently asked questions

How many degrees is a 1/12 roof pitch?

A 1/12 roof pitch is 4.76 degrees.

What is the multiplier for a 1/12 pitch?

The pitch multiplier for 1/12 is 1.0035. Multiply the footprint area or horizontal run by it to get the sloped area or rafter length.

Can you put shingles on a 1/12 roof?

No. Below 2/12, use a membrane, roll roofing or low-slope metal.

Is a 1/12 roof walkable?

Generally yes, in dry conditions with proper footwear and fall protection where required.

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.