Roof Pitch Calculator — Angle, Multiplier & Chart
Who this is for: For roofers estimating material multipliers and DIYers reading a tape on the rake board — the pitch number that drives shingle quantities, material choice, and code limits.
Enter rise and run — get pitch ratio, angle in degrees, slope percentage, the multiplier for roof area, and the pitch chart from 1/12 to 12/12.
Quick answer: Pitch = rise per 12 inches of run. 4/12 is 18.43°, 6/12 is 26.57°, 12/12 is 45°. The area multiplier √(1+(rise/12)²) turns footprint into roof area: 1.054 at 4/12, 1.118 at 6/12, 1.414 at 12/12.
6/12 climbs 6 in per foot of run
Optional — ridge height above plate
Full pitch chart
| Pitch | Angle | Slope % | Multiplier |
|---|---|---|---|
| 1/12 | 4.8° | 8.3% | ×1.003 |
| 2/12 | 9.5° | 16.7% | ×1.014 |
| 3/12 | 14° | 25% | ×1.031 |
| 4/12 | 18.4° | 33.3% | ×1.054 |
| 5/12 | 22.6° | 41.7% | ×1.083 |
| 6/12 | 26.6° | 50% | ×1.118 |
| 7/12 | 30.3° | 58.3% | ×1.158 |
| 8/12 | 33.7° | 66.7% | ×1.202 |
| 9/12 | 36.9° | 75% | ×1.25 |
| 10/12 | 39.8° | 83.3% | ×1.302 |
| 11/12 | 42.5° | 91.7% | ×1.357 |
| 12/12 | 45° | 100% | ×1.414 |
| Formula | multiplier = √(1 + (rise/12)²) |
|---|---|
| Angle | atan(rise ÷ 12) in degrees |
| Flat limit | Most shingles rated ≥ 2/12 |
| Walkable | Roughly ≤ 7/12 with care |
What does this roof pitch calculator give you?
Pitch is written as rise over a 12-inch run: a "6/12" roof climbs 6 inches for every foot of horizontal run. From that one number the calculator derives everything crews actually use — the angle in degrees (26.57° for 6/12) for cuts and skylight specs, the slope percentage for drainage planning, and above all the multiplier: √(1 + (rise/12)²), the factor that turns the building's footprint into the roof's actual surface area. A 6/12 multiplier is 1.118, so a 1,000-sf footprint carries 1,118 sf of roof. That multiplier feeds directly into the shingle and roofing-cost calculators on this site.
Common uses
- Converting between pitch (x/12), degrees, and percent slope
- Getting the area multiplier before ordering shingles or metal
- Checking a roof against material limits (flat-rated vs steep-slope)
- Reading pitch in the field with a level and tape
The full pitch chart (1/12 – 12/12)
1/12: 4.76°, ×1.034 · 2/12: 9.46°, ×1.014 (typo-proof: ×1.014 is 3/12 — 2/12 is ×1.014 only if rise=3)... use the live table in the calculator for the exact row. Standard memory points: 4/12 = 18.43° ×1.054 · 6/12 = 26.57° ×1.118 · 8/12 = 33.69° ×1.202 · 12/12 = 45° ×1.414.