12/12 Roof Pitch

A 12/12 roof rises 12 inches for every 12 inches of horizontal run: 45.00°, a 100.0% slope, and 41.4% more surface than its footprint.

12/12 pitch at a glance
Measure	12/12 value
Angle	45.00°
Slope percent	100.0%
Rise per foot of run	12 in
Pitch multiplier (area factor)	1.4142
Hip/valley factor	1.7321
Common rafter length per foot of run	17"
Plumb cut / seat cut	45.0° / 45.0°

Where you see a 12/12 roof

Typical uses: cape cods, Tudors, A-frame-style cabins and steep gables. A 12/12 roof rises one foot for every foot of run, so it sits at exactly 45 degrees. The multiplier is √2 (1.414): the roof has 41% more area than the footprint, and every rafter is 1.414 times its run. It is not walkable without equipment.

Roof area at 12/12

12/12 formulas

Angle = arctan(12 ÷ 12) = 45.00° Multiplier = √(12² + 12²) ÷ 12 = 1.4142 Roof area = footprint × 1.4142 Rafter = run × 1.4142 Ridge height = run × 12 ÷ 12

Worked examples

Roof area. A 48 × 30 ft house with 1 ft overhangs has a 50 × 32 = 1,600 sq ft footprint. At 12/12: 1,600 × 1.4142 = 2,263 sq ft, or 22.6 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 × 1.4142 = 19' 8-1/2"; add an 18" overhang (2' 1-7/16" along the slope) for 21' 10". The ridge sits 14' 0" above the plate line. Try other spans in the rafter calculator.

12/12 rafter lengths and ridge heights

Common rafters at 12/12, measured to the center of the ridge
Building span	Run	Rafter (no overhang)	Ridge rise
16 ft	8 ft	11' 3-3/4"	8' 0"
20 ft	10 ft	14' 1-11/16"	10' 0"
24 ft	12 ft	16' 11-5/8"	12' 0"
28 ft	14 ft	19' 9-9/16"	14' 0"
32 ft	16 ft	22' 7-1/2"	16' 0"
36 ft	18 ft	25' 5-1/2"	18' 0"

Roof area by footprint at 12/12

Footprint to roof area at 12/12
Footprint (incl. overhang)	Roof area	Squares
1,000 sq ft	1,414 sq ft	14.1
1,500 sq ft	2,121 sq ft	21.2
2,000 sq ft	2,828 sq ft	28.3
2,500 sq ft	3,536 sq ft	35.4
3,000 sq ft	4,243 sq ft	42.4

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.

← 11/12 pitch · All pitches in degrees

Frequently asked questions

How many degrees is a 12/12 roof pitch?

A 12/12 roof pitch is 45.00 degrees.

What is the multiplier for a 12/12 pitch?

The pitch multiplier for 12/12 is 1.4142. Multiply the footprint area or horizontal run by it to get the sloped area or rafter length.

Can you put shingles on a 12/12 roof?

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

Is a 12/12 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.