Column Load Calculator Formula
Understand the math behind the column load calculator. Each variable explained with a worked example.
Formulas Used
Maximum Load
max_load_lbs = cross_area * allowable_stressMaximum Load
max_load_kips = cross_area * allowable_stress / 1000Cross-Section Area
area = cross_areaVariables
| Variable | Description | Default |
|---|---|---|
col_width | Column Width(in) | 6 |
col_depth | Column Depth(in) | 6 |
allowable_stress | Allowable Compressive Stress(psi) | 1000 |
cross_area | Derived value= col_width * col_depth | calculated |
How It Works
Column Axial Load
P = A x Fc
Where A is the cross-sectional area and Fc is the allowable compressive stress. This applies to short columns where buckling is not a concern. For slender columns, the Euler buckling formula must be used to reduce the allowable load.
Worked Example
6x6 wood column with 1,000 psi allowable stress.
- 01Area = 6 x 6 = 36 sq in
- 02Max load = 36 x 1000 = 36,000 lbs = 36 kips
- 03Note: actual lumber is 5.5 x 5.5 so use 30.25 sq in.
Frequently Asked Questions
When is a column considered short vs slender?
For wood, if the slenderness ratio (Le/d) is less than about 11, it is a short column. Steel columns use KL/r; below about 40 is considered short. Slender columns require buckling analysis.
What is the actual size of a 6x6 post?
Nominal 6x6 lumber actually measures 5.5 x 5.5 inches. Always use the actual dimensions for structural calculations.
Learn More
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Open Column Load Calculator