Roof Slope Calculator — Calculate Roof Pitch, Rafter Length & Cost

Roof Slope Calculator

Calculate roof slope (pitch), rafter length, materials needed, and project cost. Understand how roof pitch affects material requirements and installation costs.

Step 1: Roof Dimensions

Rise: 6 ft
Run: 15 ft
Pitch: 4:12 (18.4°)

Understanding Roof Pitch

Roof pitch is expressed as a ratio of vertical rise to horizontal run. A 4:12 pitch means 4 inches of rise for every 12 inches of run. Steeper pitches require more materials and affect installation costs.

Step 2: Material & Cost

$ per square
1 square = 100 sq ft of roofing
$ per square
10%

About Roofing Squares

Roofing materials are measured in “squares” – each square equals 100 square feet. Steeper roofs have more surface area than their footprint, requiring more materials.

Roof Slope Calculation Results

Summary
Material Comparison
Cost Analysis

Total Estimated Roof Cost

$4,320
Roof Area: 1,200 sq ft (12 squares)
Roof Pitch
4:12 (18.4°)
Rafter Length
16.2 ft
Material Cost
$1,440
Labor Cost
$1,800
Roof Area
1,200 sq ft
Roof Squares
12 squares
Cost per Square
$360
Cost per sq ft
$3.60

Roofing Material Comparison

Material Type Material Cost Labor Cost Total Cost Lifespan

Roofing Cost Analysis

Roof Slope Formulas

Pitch = Rise ÷ Run × 12

Roof pitch is calculated by dividing the rise by the run, then multiplying by 12 to get the X:12 ratio. Rafter length = √(rise² + run²). Roof area = rafter length × roof length × number of sides.

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