ARCHITECTURE
Roof Slope Calculator
Pitch · Angle · Rise · Run · Rafter · Area — in imperial or metric
4:12
18.4°
Enter any two values
in
in
°
Leave blank to compute
Pitch
—
:12
Slope angle
—
°
Rise per 12" run
—
in
Slope percentage
—
%
Hypotenuse (rafter)
—
in
Pitch = rise / run × 12 | θ = atan(rise / run)
Triangle diagram
Right triangle representation
Slope comparison
Relative steepness
Rafter & area
m
ratio
Format: rise:run (e.g., 4:12, 6:12, 1:1)
m
Rafter length (total)
—
m
Roof area (plan)
—
m²
Slope factor
—
×
Actual roof area
—
m²
Rafter = √((span/2)² + rise²) + overhang
Roof geometry
Gable roof cross-section
Common roof pitches
| Pitch (rise:12) | Angle (°) | Slope factor | Description | Use |
|---|---|---|---|---|
| 1:12 | 4.8 | 1.003 | Nearly flat | Commercial |
| 3:12 | 14.0 | 1.031 | Low slope | Industrial |
| 4:12 | 18.4 | 1.054 | Low pitch | Residential |
| 6:12 | 26.6 | 1.118 | Conventional | Residential |
| 8:12 | 33.7 | 1.202 | Steep | Residential |
| 10:12 | 39.8 | 1.302 | Very steep | Snow regions |
| 12:12 | 45.0 | 1.414 | 45° pitch | Traditional |
Slope factor = √(1 + (rise/run)²)