Rafter Calculator
Determine exact roof rafter cut lengths, rise height, bird's mouth seat/heel cuts, framing angles, and material estimates instantly.
1. Rafter Specifications
4 inches of rise per 12 inches of run.
Building Span (feet)
Ridge Board Thickness (inches)
Horizontal Overhang / Eaves (inches)
Nominal Lumber Size
Bird's Mouth Seat Cut (inches)
Roof Length (feet)
Rafter Spacing (O.C.)
Price per Board ($)
Waste Allowance (10%)
Calculated Rafter LengthCommon Gable
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PLUMB CUT ANGLE18.4°Angle at Ridge/Fascia
LEVEL PLATE CUT ANGLE71.6°Seat Angle at Top Plate
Roof Profile VisualizerScale: 1.5705x
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Detailed Cut Information
Theoretical Slope Length:12' 7" (12.583 ft)
Overhang Slope Length:1' 0 5/8" (1.054 ft)
Total Vertical Rise:3' 11 3/4" (3.979 ft)
Height Above Plate (HAP):4 5/8" (4.63 in)
Heel Cut Depth (Vertical):1 3/16" (1.17 in)
Materials & Pricing Summary
RAFTERS NEEDED48 pcsSpacing: 16 in O.C.
ORDER QUANTITY53 pcsIncl. 10% waste (5 pcs)
RECOMMENDED BOARD LENGTHPurchase 14 ft Boards
14 ft BoardEstimated Material Cost:$662.50