Free roof area calculator
Free online calculator. Measure roof planes, subtract openings and add an allowance.
In roof-plane mode, measure length and width along the sloped surface. The number of planes multiplies the area of one rectangle. In projection mode, enter the full horizontal rectangular projection of the roof including overhangs; all planes must have the same pitch. Area = projection area / cos(α). Calculate different pitches separately. Enter openings in m² of sloped surface, not projection. The section list totals different roof planes and pitches. Add each section once. Surface mode uses sloped dimensions; projection mode uses horizontal dimensions. Triangle and trapezoid heights are perpendicular to their bases in the same plane. Openings always use m² of sloped surface. Sections must not overlap.
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