10/12 Roof Pitch
A 10/12 pitch rises 10 inches for every 12 inches of run: 39.81°, a 83.3% slope and a multiplier of 1.302.
- Angle39.81°
- Percent slope83.3%
- Multiplier1.3017
- Rafter per ft run15.62 in
Roof pitch
10/12 pitch
39.8° · 83.3% · ×1.302
10/12 is 39.81°, a 83.3% slope, and the roof is 30.2% larger than its footprint.
- Angle39.81°
- Percent slope83.3%
- Pitch multiplier1.3017
- Hip and valley factor1.6415
- Rafter per foot of run15.62 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 10/12 pitch looks like
At 10/12 the roof is very steep, steeper than the range GAF says covers most US homes. Expect more surface area, careful staging and more attention to safety. The roof rises 10 inches for every 12 inches of run. That is a 39.81° angle, a 83.3% slope and a roof surface 30.2% larger than its footprint.
Roof area at 10/12
Multiply the footprint by 1.3017. For common footprints, with no overhang and 10% extra on the shingles:
| Footprint | Roof area | Squares | Bundles with 10% extra |
|---|---|---|---|
| 1,000 sq ft | 1,302 sq ft | 13.0 | 43 |
| 1,500 sq ft | 1,953 sq ft | 19.5 | 65 |
| 2,000 sq ft | 2,603 sq ft | 26.0 | 86 |
| 2,500 sq ft | 3,254 sq ft | 32.5 | 108 |
| 3,000 sq ft | 3,905 sq ft | 39.1 | 129 |
Rafter length at 10/12
Each foot of run adds 15.62 inches of common rafter, or 1.6415 ft of hip or valley rafter per foot of common run. For some typical runs, measured to the ridge centerline:
| Run | Rise | Rafter length |
|---|---|---|
| 4 ft | 3 ft 4 in | 5 ft 2½ in |
| 6 ft | 5 ft 0 in | 7 ft 9¾ in |
| 8 ft | 6 ft 8 in | 10 ft 5 in |
| 10 ft | 8 ft 4 in | 13 ft 0¼ in |
| 12 ft | 10 ft 0 in | 15 ft 7½ in |
| 14 ft | 11 ft 8 in | 18 ft 2⅝ in |
| 16 ft | 13 ft 4 in | 20 ft 9⅞ in |
Roofing materials at 10/12
Shingles and metal both work, but check the manufacturer’s instructions for steep-slope fastening and staging. 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 10/12 roof?
OSHA classes any roof over 4 in 12 as steep. At 10/12 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 10/12 roof pitch?
39.81 degrees, a 83.3% slope.
What is the multiplier for a 10/12 roof?
1.3017. Multiply the footprint area by it to get roof area. The hip/valley factor is 1.6415.
How much roof area does a 10/12 pitch add?
30.2% over the footprint. A 2,000 sq ft footprint becomes 2,603 sq ft of roof, 26.0 squares.
Is 10/12 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 10/12 roof rise over a 12-foot run?
10 feet. Over a 12-foot run the roof climbs 10 feet, which is 15 ft 7½ in of rafter along the slope.
Other roof pitches
Related
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)