8/12 Roof Pitch

A 8/12 pitch rises 8 inches for every 12 inches of run: 33.69°, a 66.7% slope and a multiplier of 1.202.

Angle33.69°
Percent slope66.7%
Multiplier1.2019
Rafter per ft run14.42 in

Roof pitch

8/12 pitch

33.7° · 66.7% · ×1.202

8/12 is 33.69°, a 66.7% slope, and the roof is 20.2% larger than its footprint.

Angle33.69°
Percent slope66.7%
Pitch multiplier1.2019
Hip and valley factor1.5635
Rafter per foot of run14.42 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 8/12 pitch looks like

At 8/12 the roof is steep enough to shed water and snow quickly, and it has 14% more surface than a 4/12 roof on the same footprint. The roof rises 8 inches for every 12 inches of run. That is a 33.69° angle, a 66.7% slope and a roof surface 20.2% larger than its footprint.

Roof area at 8/12

Multiply the footprint by 1.2019. For common footprints, with no overhang and 10% extra on the shingles:

Roof area and shingles at 8/12
Footprint	Roof area	Squares	Bundles with 10% extra
1,000 sq ft	1,202 sq ft	12.0	40
1,500 sq ft	1,803 sq ft	18.0	60
2,000 sq ft	2,404 sq ft	24.0	80
2,500 sq ft	3,005 sq ft	30.0	100
3,000 sq ft	3,606 sq ft	36.1	119

Rafter length at 8/12

Each foot of run adds 14.42 inches of common rafter, or 1.5635 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 8/12
Run	Rise	Rafter length
4 ft	2 ft 8 in	4 ft 9¾ in
6 ft	4 ft 0 in	7 ft 2½ in
8 ft	5 ft 4 in	9 ft 7⅜ in
10 ft	6 ft 8 in	12 ft 0¼ in
12 ft	8 ft 0 in	14 ft 5⅛ in
14 ft	9 ft 4 in	16 ft 9⅞ in
16 ft	10 ft 8 in	19 ft 2¾ in

Roofing materials at 8/12

Shingles and metal both work. 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 8/12 roof?

OSHA classes any roof over 4 in 12 as steep. At 8/12 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 8/12 roof pitch?

33.69 degrees, a 66.7% slope.

What is the multiplier for a 8/12 roof?

1.2019. Multiply the footprint area by it to get roof area. The hip/valley factor is 1.5635.

How much roof area does a 8/12 pitch add?

20.2% over the footprint. A 2,000 sq ft footprint becomes 2,404 sq ft of roof, 24.0 squares.

Is 8/12 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 8/12 roof rise over a 12-foot run?

8 feet. Over a 12-foot run the roof climbs 8 feet, which is 14 ft 5⅛ 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)