Gambrel Roof Calculator — Calculate Your Roof Dimensions & Materials

Gambrel Roof Calculator

Calculate your gambrel roof dimensions with our comprehensive calculator. Estimate rafter lengths, angles, roof area, and materials needed for construction.

Step 1: Roof Dimensions

Enter as X in X/12 pitch ratio
Enter as X in X/12 pitch ratio

Understanding Gambrel Roof

A gambrel roof has two different slopes on each side. The lower slope is steeper than the upper slope. Common lower pitches range from 6/12 to 8/12, while upper pitches range from 12/12 to 20/12.

Step 2: Materials & Cost

About Gambrel Roof Construction

Gambrel roofs provide more interior space and are commonly used for barns, sheds, and colonial-style homes. Proper calculation ensures structural integrity and accurate material estimation.

Gambrel Roof Results

Summary
Roof Comparison
Materials

Estimated Total Cost

$1,836.00
Based on 24×30 building with 6/12 and 12/12 pitches
Total Roof Area
1,224 sq.ft
Lower Rafter Length
13.42 ft
Upper Rafter Length
16.97 ft
Rafter Quantity
46

Roof Type Comparison

Roof Type Total Area Material Cost Labor Complexity

Materials Breakdown

Gambrel Roof Formula

Rafter Length = √(Run² + Rise²)

To calculate rafter lengths for gambrel roofs: 1) Calculate rise for each section using pitch ratio, 2) Calculate run for each section, 3) Use Pythagorean theorem to find rafter length. Total roof area = (Lower Rafter Length + Upper Rafter Length) × Building Length × 2.

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