Calculator
What is roof pitch?
Roof pitch describes how steep a roof is. It is usually expressed as a ratio, such as 6:12, which means the roof rises 6 inches for every 12 inches of horizontal run. Pitch can also be expressed in degrees or as a percentage slope. Roof pitch determines which roofing materials are code-compliant, how much surface area you need to cover, and how safely workers can move on the roof.
Common roof pitches reference
| Pitch (X:12) | Degrees | Slope % | Coefficient | Walkability |
|---|---|---|---|---|
| 2:12 | 9.5° | 16.7% | 1.014 | Easy |
| 3:12 | 14.0° | 25.0% | 1.031 | Easy |
| 4:12 | 18.4° | 33.3% | 1.054 | Easy |
| 5:12 | 22.6° | 41.7% | 1.083 | Moderate |
| 6:12 | 26.6° | 50.0% | 1.118 | Moderate |
| 7:12 | 30.3° | 58.3% | 1.158 | With care |
| 8:12 | 33.7° | 66.7% | 1.202 | Steep |
| 9:12 | 36.9° | 75.0% | 1.250 | Steep |
| 10:12 | 39.8° | 83.3% | 1.302 | Steep |
| 12:12 | 45.0° | 100.0% | 1.414 | Steep |
Formulas used
- Pitch ratio (X:12): (Rise ÷ Run) × 12
- Angle (degrees): arctan(Rise ÷ Run) × (180 ÷ π)
- Slope percentage: (Rise ÷ Run) × 100
- Rafter length: √(Rise² + Run²)
- Slope coefficient: √(1 + (Rise ÷ Run)²)
How to use this calculator
- Choose your input mode: Rise & Run, Angle, or Pitch Ratio (X:12).
- Enter your measurements. If using Rise & Run, select your unit (ft, in, m, cm).
- The results update instantly as you type — no submit button needed.
- Click "Copy shareable link" to share your calculation with a colleague or contractor.
Frequently asked questions
What is a walkable roof pitch?
A roof pitch of 6:12 or less is generally considered walkable for most people. Above 7:12, roof jacks or fall protection are typically required. Above 9:12, most crews consider the roof non-walkable without special equipment.
What is the minimum roof pitch for asphalt shingles?
Asphalt shingles require a minimum pitch of 2:12 with double underlayment. Below 2:12, you need a different roofing system such as EPDM, TPO, or modified bitumen.
How do I measure roof pitch from the attic?
Hold a level horizontally against the underside of a rafter. Mark 12 inches along the level from where it touches the rafter. Measure vertically from that 12-inch mark up to the rafter. That vertical measurement in inches is your rise over 12 inches of run.
What is the slope coefficient and why does it matter?
The slope coefficient converts horizontal footprint area to actual sloped roof surface area. For example, a 6:12 pitch has a coefficient of 1.118, meaning a 2,000 sq ft footprint has 2,236 sq ft of actual roof surface. This is the number you need for accurate material ordering.
What is the most common residential roof pitch?
The most common US residential pitch is 6:12 (26.6°), which balances drainage, material cost, and walkability. In snowy regions, 8:12 to 10:12 is more common. In the UK and Europe, pitches are often expressed in degrees rather than X:12 ratios.