Roof Pitch Calculator
Calculate roof pitch, angle, and rafter dimensions with ease.
Calculation Results
Real-TimeRoof Pitch Examples
Typical use: Ranch homes, porch roofs, and additions where height is limited.
Materials: Shingles require double underlayment at 3:12; standing-seam metal is rated from 1/2:12.
Typical use: The most common range on modern US single-family homes.
Materials: All standard asphalt shingles, metal panels, and concrete or clay tile.
Typical use: Tudor, Cape Cod, and A-frame styles; sheds snow and rain fastest.
Materials: Slate, heavy architectural shingles, and interlocking metal — specialist installation.
How to Measure Roof Pitch
All you need: a 12-inch carpenter’s level and a tape measure.
- 1Find a common rafter. Find an accessible, straight common rafter board — not a hip or valley rafter, which run diagonally and have a flatter slope.
- 2Position the level. Place the end of a 12-inch or 24-inch carpenter's level flush against the underside of the rafter.
- 3Level the bubble. Pivot the level until the spirit bubble is perfectly centered between the index lines, so the level is truly horizontal.
- 4Measure the rise. Measure vertically with a tape measure from the 12-inch mark on the level up to the bottom edge of the rafter. That measurement in inches is your X:12 pitch.
| Roofing Material | Min. Pitch | Min. Angle | Code / Installation Requirement |
|---|---|---|---|
| EPDM / TPO / PVC membrane, built-up roof (BUR) | 1/4 : 12 | 1.2° | Continuous waterproof membrane; required for low-slope decks (IBC Ch. 15) |
| Standing-seam metal | 1/2 : 12 | 2.4° | Mechanical seaming required below 3:12 |
| Asphalt shingles | 2 : 12 | 9.5° | Double underlayment required below 4:12 (IRC R905) |
| Clay & concrete tile | 2.5 : 12 | 11.8° | Double membrane on solid sheathing; battens at 4:12+ |
| Natural slate | 4 : 12 | 18.4° | Heavy framing; 3"–4" headlap |
Related Calculators
What is roof pitch?
Roof pitch is the steepness of a roof, usually expressed as a ratio (e.g., 6:12), a percentage (e.g., 50%), or an angle (e.g., 26.6°). It helps you understand how sloped your roof is and is important for design, drainage, and material choice.