10/12 Roof Pitch

A 10/12 roof rises 10 inches for every 12 inches of horizontal run: 39.81°, a 83.3% slope, and 30.2% more surface than its footprint.

10/12 pitch at a glance
Measure	10/12 value
Angle	39.81°
Slope percent	83.3%
Rise per foot of run	10 in
Pitch multiplier (area factor)	1.3017
Hip/valley factor	1.6415
Common rafter length per foot of run	15-5/8"
Plumb cut / seat cut	39.8° / 50.2°

Where you see a 10/12 roof

Typical uses: Tudor, cottage and cape-style homes with rooms in the attic. At almost 40 degrees, a 10/12 roof is a true steep-slope job. Expect staging, harnesses and a steep charge on labor. In return you get serious attic headroom, and it is common on houses with finished space or dormers upstairs.

Roof area at 10/12

10/12 formulas

Angle = arctan(10 ÷ 12) = 39.81° Multiplier = √(10² + 12²) ÷ 12 = 1.3017 Roof area = footprint × 1.3017 Rafter = run × 1.3017 Ridge height = run × 10 ÷ 12

Worked examples

Roof area. A 48 × 30 ft house with 1 ft overhangs has a 50 × 32 = 1,600 sq ft footprint. At 10/12: 1,600 × 1.3017 = 2,083 sq ft, or 20.8 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 × 1.3017 = 18' 1-11/16"; add an 18" overhang (1' 11-7/16" along the slope) for 20' 1-1/8". The ridge sits 11' 8" above the plate line. Try other spans in the rafter calculator.

10/12 rafter lengths and ridge heights

Common rafters at 10/12, measured to the center of the ridge
Building span	Run	Rafter (no overhang)	Ridge rise
16 ft	8 ft	10' 4-15/16"	6' 8"
20 ft	10 ft	13' 3/16"	8' 4"
24 ft	12 ft	15' 7-7/16"	10' 0"
28 ft	14 ft	18' 2-11/16"	11' 8"
32 ft	16 ft	20' 9-15/16"	13' 4"
36 ft	18 ft	23' 5-3/16"	15' 0"

Roof area by footprint at 10/12

Footprint to roof area at 10/12
Footprint (incl. overhang)	Roof area	Squares
1,000 sq ft	1,302 sq ft	13.0
1,500 sq ft	1,953 sq ft	19.5
2,000 sq ft	2,603 sq ft	26.0
2,500 sq ft	3,254 sq ft	32.5
3,000 sq ft	3,905 sq ft	39.1

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.

← 9/12 pitch · 11/12 pitch → · All pitches in degrees

Frequently asked questions

How many degrees is a 10/12 roof pitch?

A 10/12 roof pitch is 39.81 degrees.

What is the multiplier for a 10/12 pitch?

The pitch multiplier for 10/12 is 1.3017. Multiply the footprint area or horizontal run by it to get the sloped area or rafter length.

Can you put shingles on a 10/12 roof?

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

Is a 10/12 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.