Roof Pitch Calculator
Convert rise/run into pitch, angle, slope percentage and pitch multiplier. Optional projected footprint gives a simple surface-area estimate without pretending to model a complex roof.
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.
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.
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.