Column Load Calculator
Wood Column Capacity
Calculate the load capacity of a wood post or column
Column Tributary Load
Calculate the load a column must support based on tributary area
Formula
Allowable Load = Fc × Cp × Area | Cp = Column Stability Factor (NDS) | Tributary Load = Area × (Dead + Live Load)
Frequently Asked Questions
How much weight can a 4x4 post support?
A standard 8-foot 4×4 (3.5"×3.5") Douglas Fir #2 post can support approximately 6,000-7,000 lbs axially. Capacity decreases with height: a 12-foot 4×4 supports roughly 3,500-4,500 lbs. A 6×6 post approximately doubles the 4×4 capacity.
How do I calculate column load?
Column load = Tributary Area × Total Load Per Square Foot. Tributary area is the floor/roof area the column supports (typically half the span in each direction). Total load includes dead load (structure weight, ~10-15 PSF) plus live load (occupancy, 40 PSF residential; snow, 20-60 PSF).
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