Architecture
Wood Beam Span Calculator
Quick beam sizing for floor and roof beams. Inputs: tributary width + load + beam type. Output: max simple-span. For preliminary sizing only — final design needs an engineer's stamp.
⚠ Preliminary sizing only
Structural members supporting a building need stamped engineering. This calc estimates spans from typical fiber stresses; final design must account for deflection, connections, code-required adjustments, and load duration.
FAQ
What's tributary width? +
The strip of floor that loads onto your beam. If joists span 16' and frame into a beam in the middle, tributary width is 16/2 = 8'.
Typical loads? +
Floor: 40 psf live + 10-15 psf dead = 50-55 psf total. Roof: 20 psf live + 15 psf dead = 35 psf. Add snow load if it controls.
L/360 vs L/240? +
L/360 keeps a floor from feeling bouncy. L/240 is the bare minimum for floor joists. L/480 is for floors with tile/stone that crack with too much deflection.
LVL or 2x? +
LVL is engineered, very consistent, and 30-50% stronger psi-for-psi. Worth it for long spans or heavy loads. Solid 2x is cheaper for short spans.