Roof Area Calculator
Plan length times width, then multiply by hypot(run, rise) divided by run. That is a simple gable from a rectangular plan. Estimate only, not a full takeoff.
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How to estimate gable roof area
- Enter the rectangular plan length and width (the building footprint, not the slope length).
- Enter pitch rise and run, such as 6 and 12.
- Read plan area, the factor, and estimated roof surface in the same units squared.
- Pitch-only conversion without plan size is the roof pitch page. Not code approval.
Gable roof surface
Rectangular plan scaled by pitch
| Plan area | length × width |
|---|---|
| Area factor | hypot(run, rise) / run |
| Roof surface | plan × factor |
| Roofing square | 100 ft² in trade talk, not auto-converted here |
| Shape | Simple gable rectangle |
| Advice | Estimate only. Not structural design or code approval. |
How gable roof area is computed
Plan is length times width. Factor is hypot(run, rise) divided by run, the same idea as hypot(1, rise/run). Roof surface is plan times factor. Units stay whatever you typed for length and width.
Plan, pitch, and a roofing square
A roofing square is 100 square feet of covering in many US quotes. This page does not divide by 100. Pitch without a plan is roof pitch. Floor plan without pitch is square footage. Wall paint is paint.
Simple gable, estimate only
Hips, dormers, rakes, and double coverage at ridges are not added. Confirm with a roofer. Not code approval.
Use cases
A 40 by 24 ft plan on a 6/12 pitch, or comparing a flatter run. Sheathing waste is not included unless you raise the plan yourself.
Limits
Length and width must be greater than 0. Rise can be 0. Run must be greater than 0. CZNull does not receive the numbers.