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The Purlins for Dormers calculator computes the total number and length of purlins (roof support boards) for needed for one or more roof dormers based on the dimensions.

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)
• (n) Number of Dormers
• (pS) Purlin Spacing

Purlins for Dormers (PRLN): The calculator returns:

• (TA) Area: Total surface area of dormer(s) in square feet.
• (nP) Number of Rows : Number of rows of purlins on a single dormer.
• (pL) Purlin Length: For each row (both sides), the length of the purlin. 
• (TBL) Total Board Length: The sum of the lengths of the purlin boards

Items with units can be automatically converted to compatible units via the pull-down menu.

The Math / Science

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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.

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Roof Types

Roofing Calculators

Gable Roof Area of Gable Roof Gable Roof 4x8 Sheathing Gable Roof Sheathing Cost Purlins for a Gable Roof Metal for a Gable Roof Screws for Metal Gable Roof Shingles for a Gable Roof Gable Roof Shingle Cost Underlayment for Gable Roof Nails for Gable Sheathing Roofing Nails for Gable Roof Rafters and Ties for Roof Rafters Length	Hip Roof Surface Area of Hip Roof Sheathing for Hip Roof Shingles for Hip Roof Roofing Nails for Hip Roof Cost of Shingles for Hip Roof Metal for Hip Roof Screws for Metal Hip Roof Purlins for Hip Roof Underlayment for Hip Roof Surface area for Double Hip Roof Hip Roof Geometries	Shed Roof Bundles of Shingles for Shed Roof Cost to Shingle a Shed Roof Underlayment and Cost for Shed Roof 4x8s for Shed Roof Metal Panels (Ag Panels) for Shed Roof Screws for Metal Panel Shed Roof Purlins for Shed Roof Trusses for Shed Roof Metal for Shed Roofed Animal Run-in
Dormers Surface Area of Dormers Metal for Dormers Screws for Metal Dormers 4x8s for Dormers Shingles for Dormers Roofing Nails for Dormers Purlins for Dormers	Pyramid Hip Roof Shingles for a Pyramid Roof 4x8 Sheathing for Pyramid Roof Underlayment for Pyramid Roof Metal Panels for Pyramid Roof Purlins for Pyramid Roof Pyramid Roof Geometries	Roofing Geometries Pitch to Slope Pitch to Angle Rise over Run to Angle Gambrel Angle Interface Angle Interface Angle from Rise over Run Trusses Needed for a Roof Area of Roof Section
Gambrel Roof Gambrel Roof Surface Area Gambrel Roof Shingles  Roofing Nails for Gambrel Roof Gambrel Roof Underlayment Purlins for Gambrel Roof Gambrel Roof Metal Panels Screw for Metal Gambrel Roof Gambrel Angle