Roof Pitch Calculator
Start with X:12 pitch, measured rise and run, or a roof angle in degrees. Convert between pitch, angle, slope percentage and multiplier, with an optional simple surface-area estimate.
Continue your project estimate
Calculate rafter length from this pitch →Roof pitch formulas
pitch X:12 = rise ÷ run × 12
slope % = rise ÷ run × 100
angle = arctan(rise ÷ run)
pitch multiplier = √(1 + (rise ÷ run)²)
Example: a 6:12 roof
A 6:12 roof rises 6 units for every 12 units of horizontal run. That is a 50% slope, about 26.57°, with a pitch multiplier of about 1.118.
Convert roof angle to pitch
If you know the roof angle instead of rise and run, select Roof angle in degrees. The calculator converts the angle with rise/run = tan(angle), then expresses the same slope as X:12 pitch.
For example, an angle of about 26.565° corresponds to a 6:12 pitch. A 45° angle corresponds to a 12:12 pitch. Use measured geometry for planning when an angle reading is uncertain.
Common roof pitch reference
These values are geometric conversions for standard X:12 pitches. They do not determine whether a roof assembly, material or structural design is appropriate for a project.
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 1:12 | 4.76° | 8.33% | 1.0035× |
| 2:12 | 9.46° | 16.67% | 1.0138× |
| 3:12 | 14.04° | 25% | 1.0308× |
| 4:12 | 18.43° | 33.33% | 1.0541× |
| 5:12 | 22.62° | 41.67% | 1.0833× |
| 6:12 | 26.57° | 50% | 1.118× |
| 7:12 | 30.26° | 58.33% | 1.1577× |
| 8:12 | 33.69° | 66.67% | 1.2019× |
| 9:12 | 36.87° | 75% | 1.25× |
| 10:12 | 39.81° | 83.33% | 1.3017× |
| 11:12 | 42.51° | 91.67% | 1.3566× |
| 12:12 | 45° | 100% | 1.4142× |
Use the calculator above for non-integer pitches, a measured rise/run pair or an angle in degrees.
About the optional roof-area estimate
The calculator multiplies the horizontal projected footprint by the pitch multiplier. This is appropriate only when the roof planes share the same pitch and the footprint adequately represents the horizontal projection. Overhangs, dormers, valleys and mixed pitches require separate geometry.
From roof pitch to roofing quantity and cost
Pitch is often an input to the next planning step rather than the final answer. Use the Shingle Calculator when you need roofing squares and bundles, the roofing-squares guide when you want the area conversion explained step by step, and the Roofing Cost Calculator when you are ready to apply local material, labor, tear-off and fixed-extra rates.
Using the result correctly
Pitch, slope percentage and angle are different ways to describe the same rise-to-run relationship. The multiplier can help convert a simple horizontal projection into sloped length or area, but complex roofs with hips, valleys, dormers or unequal slopes require separate geometry rather than one whole-roof multiplier.
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