Beam Span Calculator

Select a beam size, lumber species, and tributary width to look up maximum allowable spans based on simplified IRC residential tables. Compare all beam sizes side by side.

Beam Size

Lumber Species

Floor Live Load

Tributary Width (ft)

Beam Cross-Section

Hover for details • structural cross-section

Max Allowable Span

9' 6"

9.5 ft for 2-ply 2x10

Beam Size

2-ply 2x10

SPF #2

Tributary Width

8 ft

40 PSF live load

Beam Size	Max Span	Span (ft)
2-ply 2x8	7' 6"	7.5 ft
2-ply 2x10Best value	9' 6"	9.5 ft
2-ply 2x12	11' 6"	11.5 ft
3-ply 2x10	11' 6"	11.5 ft
3-ply 2x12	13' 6"	13.5 ft
4x6 Solid	5' 6"	5.5 ft
6x6 Solid	6' 6"	6.5 ft

Consider engineered beams for longer spansIf you need to span more than these tables allow, look into LVL (laminated veneer lumber), PSL, or steel beams. Engineered beams can span significantly farther than dimensional lumber and are commonly used for headers, ridge beams, and point-load situations.

These spans are simplified approximations based on IRC tables for residential construction. Always verify with a licensed structural engineer for actual beam sizing — real-world conditions (point loads, cantilevers, multi-story, snow loads) often require engineering beyond prescriptive tables.