ROOF FRAMING GEOMETRY
Rafter Length Calculator
Calculate exact theoretical common rafter length, slope angle in degrees, vertical rise, and overhang allowances from horizontal run and roof pitch.
Rafter Length Calculator
Calculate precise theoretical rafter length, vertical rise, and overhang allowances.
feet
Horizontal distance from outside wall top plate to ridge centerline.
/ 12
inches
How Rafter Length Is Calculated
Rafter length is determined using the Pythagorean theorem where the horizontal run is one leg, the vertical rise is the second leg, and the rafter hypotenuse is the sloped length from ridge to wall plate.
Framing Formulas
Rise = Run × (Pitch ÷ 12)
Base Rafter Length = √(Run² + Rise²)
Overhang Length = √(Overhang² + (Overhang × Pitch ÷ 12)²)
Total Rafter Length = Base Rafter Length + Overhang Length