Birdsmouth Cut Calculator
Calculate the critical dimensions for a birdsmouth notch on a rafter.
Rafter & Wall Parameters
Actual width of the rafter (e.g., 2×6 = 5.5")
Actual thickness of the rafter (e.g., 2×6 = 1.5")
Depth of the notch on the wall plate
Rise per foot of run (e.g., 6/12)
Seat Cut Depth
0.00
in
Heel Stand
0.00
in
Throat Depth
0.00
in
Seat Cut Length
0.00 in
Plumb Cut Depth
0.00 in
Remaining Material
0.00 in
Status
✅ Safe
Rafter Width
0.0
inches
Rafter Depth
0.0
inches
Pitch
0/12
selected
The birdsmouth cut should not exceed 1/3 of the rafter depth for structural safety.
Heel Stand = Seat Cut × cos(θ)
Throat Depth = Rafter Width - Heel Stand