How the wood column calculator works
This free wood column calculator checks wood posts, wall studs and built-up columns by the 2018 National Design Specification for Wood Construction (NDS), the edition referenced by the Florida Building Code, 8th Edition (2023). Choose dimension lumber, posts and timbers or PSL, the size and number of plies, the height and bracing, then enter the axial load and any lateral wind load for each load case. The calculator finds the column stability factor about both axes and checks every ASCE 7-22 load combination in ASD or LRFD.
What it checks
- Axial compression fc = P/A against Fc′ with the column stability factor CP about both axes, FcE = 0.822Emin′/(le/d)² and le/d ≤ 50
- Built-up columns of 2 to 4 plies, with CP reduced by Kf = 0.6 (nailed) or 0.75 (bolted) for buckling across the laminations (NDS §15.3)
- Axial load with bending from wind on the stud or load eccentricity by NDS Eq. 3.9-3, including the amplification 1/(1 − fc/FcE1) and the beam stability factor CL
- Net uplift in tension with bending by Eq. 3.9-1 and 3.9-2, and shear from the lateral load
- Bearing of the column on a wood sill or top plate with the bearing area factor Cb
Method
Each ASCE 7-22 combination is built from your loads, with wind in both directions. In ASD the load duration factor CD comes from the shortest-duration load in the combination, so a wind combination uses CD = 1.6. In LRFD the reference values are multiplied by KF, φ and the time effect factor λ. The Capacity vs height tab gives the allowable or factored axial load from 2 to 24 ft, in the style of a stud or post load table.
Assumptions and limitations
- Rectangular solid or built-up columns pinned at both ends, with lateral load and eccentricity about the strong axis. Biaxial bending, spaced columns, tapered columns and notched studs are not covered.
- Reference design values follow the NDS 2018 Supplement Tables 4A, 4B and 4D; the PSL values are generic and must be replaced with the manufacturer's published values.
- Eccentric loads are treated as an end moment P·e rather than by NDS Eq. 15.4-1.
Frequently asked questions
How much load can a 2x6 stud carry?
It depends on the species, grade, height and bracing. A 10 ft Douglas Fir-Larch No. 2 2x6 braced by sheathing on its weak axis carries about 6,700 lb in ASD under live load, and less when wind bending is added. The calculator shows the exact value and a capacity table for every height.
What is the column stability factor CP?
CP reduces the compression strength for buckling. It depends on the slenderness le/d, the modulus Emin and the reference strength, and it approaches 1.0 for short, stocky columns.
Why does a built-up column use Kf?
Nailed or bolted laminations do not act fully as one piece when the column buckles across the laminations. NDS §15.3 reduces CP by Kf = 0.6 for nailed and 0.75 for bolted columns that meet its fastening rules.
Should wall studs be checked for wind?
Yes. Exterior studs carry gravity load and bend under wind at the same time. Enter the wind pressure times the stud spacing as w, and the calculator combines the two by NDS Eq. 3.9-3 with CD = 1.6.
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For educational and preliminary design purposes only. Always verify results with a licensed PE.