The Locolory toolkit / Roofing & Structural Framing
Convert roof pitch ratios to degrees, slope percentage, geometric common-rafter length, and surface-area multipliers for preliminary roofing estimates.
What is roof pitch and how is it measured? Roof pitch is vertical rise divided by horizontal run, commonly written as inches of rise per 12 inches of run. A 6:12 pitch has a 26.57° slope angle.
Pure client-side trigonometric calculations. Geometry and material estimate only—not structural sizing, a cut plan, or code approval.
Angle
26.57°
Slope
50.0%
Multiplier
1.118
Ridge rise
6.00 ft
Rafter to fascia
14.53 ft
Roofing squares
13.42
Surface estimate: 1342 ft² before waste. Have a qualified professional size rafters and verify loads, cuts, connections, roofing assembly, and local code.
In an accessible attic, hold a level horizontally against a rafter, mark a 12-inch run, and measure vertically to the rafter. That rise is the X in X:12. Avoid climbing a roof without appropriate training and fall protection.
Field conditions, ridge details, birdsmouth cuts and framing connections are outside this geometric estimate.
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 1:12 | 4.76° | 8.3% | 1.003 |
| 2:12 | 9.46° | 16.7% | 1.014 |
| 3:12 | 14.04° | 25.0% | 1.031 |
| 4:12 | 18.43° | 33.3% | 1.054 |
| 5:12 | 22.62° | 41.7% | 1.083 |
| 6:12 | 26.57° | 50.0% | 1.118 |
| 7:12 | 30.26° | 58.3% | 1.158 |
| 8:12 | 33.69° | 66.7% | 1.202 |
| 9:12 | 36.87° | 75.0% | 1.250 |
| 10:12 | 39.81° | 83.3% | 1.302 |
| 11:12 | 42.51° | 91.7% | 1.357 |
| 12:12 | 45.00° | 100.0% | 1.414 |
| 13:12 | 47.29° | 108.3% | 1.474 |
| 14:12 | 49.40° | 116.7% | 1.537 |
| 15:12 | 51.34° | 125.0% | 1.601 |
| 16:12 | 53.13° | 133.3% | 1.667 |
| 17:12 | 54.78° | 141.7% | 1.734 |
| 18:12 | 56.31° | 150.0% | 1.803 |
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Many residential roofs fall around 4:12 to 9:12, but there is no single standard. Architecture, roof covering, climate, drainage, wind and snow design, and local rules all affect the appropriate pitch.
The 2024 IRC permits asphalt shingles at 2:12 or greater and requires the specified two-layer underlayment treatment from 2:12 up to 4:12. The adopted local code and the selected manufacturer's instructions control.
Multiply horizontal plan area by √(1 + (rise ÷ run)²). For X:12 pitch, that becomes √(1 + (X ÷ 12)²). Complex roofs still require separate planes and allowances for waste.
There is no universal pitch. The roof system's minimum slope, drainage details, local design snow load, drifting, wind and manufacturer instructions must be evaluated by a qualified local professional.