Beam Size Calculator
Calculate Beam Size
Estimate beam size for residential applications
Formula
Total Load = Tributary Width x Load x Span | Moment = wL^2/8 | Required S = Moment / Fb
Frequently Asked Questions
How do I size a beam for a residential floor?
Calculate the total load (tributary width x floor load x span), then determine the required section modulus. For residential floors, use 40 psf live + 10 psf dead = 50 psf total. Match the required section modulus to available beam sizes.
What is tributary width?
Tributary width is the distance from the beam to the midpoint of the spans on either side. If joists span 16 feet on one side and 12 feet on the other, the tributary width is (16/2) + (12/2) = 14 feet.
Do I need an engineer for a load-bearing beam?
Yes. While this calculator provides estimates, load-bearing beams are structural elements that require engineering calculations considering deflection, shear, bearing, and local building codes. Always get professional engineering for structural work.
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