How this calculator works
For a simple rectangular header, the required depth is the largest depth from elastic bending, rectangular-section shear and a deflection ratio. Reverse mode uses the same equations to estimate span. Uniform loading is assumed; a point load from a girder or roof member requires a different model. Width is the actual total width of plies that act together.
Formula
hb=sqrt[3wL^2/(4bFb)]; hv=3wL/(4bFv); hd=[5wL^3 r/(32Eb)]^(1/3); required h=max(hb,hv,hd). I=bh^3/12 and S=bh^2/6.
Worked example
For a 1.2 m opening, 89 mm width, 3000 N/m load, E=10 GPa, Fb=10 MPa, Fv=1 MPa and L/360, bending requires about 60.34 mm depth and deflection about 68.94 mm. Select a real product and check the complete design.
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Frequently asked questions
Does a 4 x 6 label define the section?
No. Enter actual dimensions. Nominal and surfaced sizes differ, and engineered wood uses manufacturer dimensions.
Where do I get the line load?
Determine all tributary roof, floor, wall and self-weight loads for the applicable load combinations. This page does not derive those loads.
Does the result include jack studs and bearing?
No. Results are estimates and are not a substitute for a licensed engineer. Bearing, connections, stability, local code requirements and all applicable load combinations need separate checks.