Home Improvement
Roof surface area from the footprint
The pitch multiplier converts the plan area into the sloped surface area.
The Formula
roof area = length x width x pitch multiplier
The pitch multiplier converts the plan area into the sloped surface area.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| roof area | Surface area | sq ft | The sloped area to be covered, in square feet. |
| length, width | Footprint | feet | The plan dimensions of the roof, in feet. |
| r | Pitch rise | inches | Inches of rise per twelve inches of run. |
What Each Symbol Means
roof areasq ft
Surface area
The sloped area to be covered, in square feet.
length, widthfeet
Footprint
The plan dimensions of the roof, in feet.
rinches
Pitch rise
Inches of rise per twelve inches of run.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate shingles needed page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Shingles Needed, filed under Everyday Life. Every number the guide produces comes from substituting into this one line.