Dormer Geometries

The Dormer Geometries calculator computes the diagram measurements for a dormer based on the dormer width, depth, pitch of the dormer and pitch of the roof.

INSTRUCTIONS: Choose units and enter the following:

• (DD) Dormer Depth
• (DW) Dormer Width
• (P₂) Pitch of Dormer Gable (choose pitch from list)
• (P₁) Pitch of Main Roof (choose pitch from list)

Dormer Geometries (DG): The calculator returns the lengths in inches as follows: 

• (h) Height of Dormer
• (x) Edge Length of Dormer
• (y) Ridge Length of Dormer
• (k) Prominence of Dormer
• (j) Valley Length of Dormer

The Math / Science

Dormers can be small or large, but if they conform to the basic shapes below, the math still works.

Dormer Calculators

• Surface Area of Dormers: This computes the roofing surface area for dormers based on the dimensions and number of dormers.
• Metal for Dormers: This computes the metal roof materials (panels, ridge cap and trim) for one or more roof dormers based on the dimensions
• Screws for Metal Dormers: This computes the number of metal panels screws needed for one or more roof metal paneled dormers based on the dimensions.
• 4x8s for Dormers: This computes the number of 4x8 sheathing needed for one or more roof dormers based on the dimensions.
• Shingles for Dormers: This computes the number of shingle bundles needed for one or more roof dormers based on the dimensions. It also includes ridge shingles, valley lengths for flashing, and roofing nails.
• Underlayment for Dormers: This computes the amount of underlayment needed and estimates the cost of underlayment materials.
• Roofing Nails for Dormers: This computes the number and weight of roofing nails needed for one or more roof dormers based on the dimensions.
• Purlins for Dormers: This computes the total number and length of purlins (roof support boards) for needed for one or more roof dormers based on the dimensions.
• Dormer Geometries: This computes the diagram measurements for a dormer based on the dimension.

Roof Types

Roofing Calculators