Roof Section Area

The Roof Section Area calculator computes the area (square feet), and number of bundles of shingles for a roof section based on the dimensions (see diagram) where the top and bottom are roughly parallel.  

INSTRUCTIONS: Choose units and enter the following:

• (T) Top Length
• (B) Bottom Length
• (R) Right Side Length
• (L) Left Side Length

Roof Section Area (A): The calculator returns the area in square feet.  However, this can be automatically converted to compatible units via the pull-down menu.  The calculator also returns:

• (nAB) Number of Architectural Shingle Bundles (32.8 ft²) 
• (nSB) Number of Standard Shingle Bundles (33.33 ft²)
• (nRN) Number of Roofing Nails under Normal and High Wind Conditions.
• (h) Perpendicular Height (see diagram)

The Math / Science

The surface area of the Roof Section described above is equal to the area of a trapezoid.  The important aspect is that the top (T) and bottom (B) lines are roughly parallel, no two sides are the same length, and no one side is greater than the sum of the other three.  The top or the bottom can be longer.

Roofing Geometries Calculators

• Pitch to Slope: This converts pitch (e.g., 4/12) to slope.
• Pitch to Angle: This converts pitch (e.g., 10/12) to an angle in degrees.
• Rise over Run to Angle: This converts rise over run to an angle in degrees.
• Gambrel Angle: Computes the bend at the intersection of two slope as in a gambrel roof.
• Interface Angle: This computes the interface angle between two sloped surfaces.
• Interface Angle from Rise over Run: This computes the interface angle based on two rises and runs.
• Trusses Needed for a Roof: This computes the number of trusses needed for a roof based on the ridge length and truss spacing
• Roof Section Area: This computes the surface area of an irregular shaped section of a roof.
• Gable Roof Geometries: This computes the lengths and measurements for a gabled roof based on the ridge length, pitch, span and overhang.
• Dormer Geometries: This computes the measurements for a gable dormer based on the dimension of the dormer and main roof..
• Hip Roof Geometries: This the metrics associated with a hip roof based on the dimensions.
• Double Hip Roof Geometries: This compute the lengths of the dimensional lines where one hip roof intersects another such as in a dormer.
• Pyramid Hip Roof Geometries: This computes the lengths and dimensional lines of a pyramid roof.
• Gambrel Pitch Angles: This computes the pitch angles and rafter lengths in a gambrel roof bases on the span, total height, and height and width of the loft.
• Gambrel Rafter Lengths. This computes the upper and lower rafter lengths, attic width and total height under a gambrel roof based on the upper and lower pitch, span and loft height.
• Rafter Length: This computes the length of the rafters based on the span, pitch and overhang.
• Corrugation Factor: This computes the material length associated with a structural length using corrugated material.

Roof Types

Roofing Calculators