Roof Pitch Calculator
To find roof pitch, measure the vertical rise over 12 inches of horizontal run. A roof rising 6 inches per 12 inches of run is a 6:12 pitch (about 26.6°). Divide rise by run and multiply by 12 for the pitch, then use the slope multiplier to convert your footprint to actual roof area.
- Most common pitch
- 6:12
- Walkable up to
- ~6:12
- Steep
- 9:12+
Your measurements
Vertical rise you measured.
Horizontal run — usually 12 in.
Enter your measurements
Fill in the fields to see your estimate.
The formula
Pitch = (Rise ÷ Run) × 12 ; Angle = arctan(Rise ÷ Run) ; Area multiplier = √(Rise² + Run²) ÷ RunHow to calculate it manually
- 1
Measure the run
Mark 12 inches horizontally from a level held against the roof or a rafter.
- 2
Measure the rise
Measure straight down from the 12-inch mark to the roof surface.
- 3
Read the pitch
The rise over 12 is your pitch — e.g. 6 inches down = 6:12.
- 4
Convert to area
Multiply your roof's footprint by the slope multiplier for the true surface area.
Example calculation
A 6-inch rise over a 12-inch run = 6:12 pitch, about 26.6°, with a 1.118 area multiplier.
Common roof pitches
Pitch, angle, and the multiplier used to turn footprint into roof area.
| Pitch | Angle | Area multiplier | Type |
|---|---|---|---|
| 3:12 | 14.0° | 1.031 | Low slope |
| 4:12 | 18.4° | 1.054 | Gentle, walkable |
| 6:12 | 26.6° | 1.118 | Most common |
| 8:12 | 33.7° | 1.202 | Steep |
| 12:12 | 45.0° | 1.414 | Very steep |
Common roof pitch estimating mistakes
Measuring the wrong run
Pitch is always rise over a 12-inch run. Measure a true 12 inches horizontally with a level, not along the slope.
Confusing pitch and angle
6:12 is a pitch (rise:run), not 6 degrees. Use the angle output when you need degrees.
Ignoring the multiplier
A sloped roof's real area is larger than its footprint — always apply the multiplier before ordering material.
Frequently asked questions
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