2x10 southern pine floor
Typical residential planning lookup.
16.2 ftSource-indicated max spanfloor joist calculator
Floor Joist Calculator
Floor joist span depends on species, grade, size, spacing, load, deflection, bearing, notches, holes, and local code.
Inputs
Results
Immediate estimateSource-indicated max span16.2 ftProposed span is within this limited lookup.
Proposed span14 ft
Spacing16 in o.c.
Joist size2x10
ResultWithin lookup
Review the limitations before using this result for planning.
This MVP lookup is limited to selected species, sizes, spacings, and simple loading assumptions. Do not extrapolate.
Diagram
Floor joist span
A proposed clear span is checked against a limited residential floor lookup.
- Bearing
- Joist span
- Spacing
How this calculator works
Select species group, joist size, and proposed span to compare against a limited 16-inch-on-center floor joist lookup.
Limited table
The MVP covers selected 16-inch-on-center combinations and does not interpolate between source rows.
Comparison
The calculator reports the source-indicated maximum and whether the proposed clear span is within that limited lookup.
Engineering caution
A real floor design should also consider vibration, concentrated loads, bearing, openings, and alterations.
Lookup
match species group + size + spacing to supported rowComparison
proposed clear span <= source-indicated spanAssumptions
- Use: Residential floor joist planning under a simplified 40 psf live load and 10 psf dead load assumption.
- Limits: Deflection, grade, holes/notches, bearing, vibration, and local amendments are not fully checked.
Worked examples
Long 2x8 floor span
Shows an exceeds-lookup result.
11.7 ftSource-indicated max spanFAQ
Is this a structural design tool?
No. It is a cautious planning lookup for selected common cases.
Why only 16-inch spacing?
The MVP keeps the lookup narrow to avoid implying broader coverage than the data model supports.
Does it account for holes and notches?
No. Holes, notches, and bored utilities require separate code checks.
Sources and review
- 2021 International Residential Code, International Code Council, 2021. Accessed 2026-07-16.
- Wood Handbook: Wood as an Engineering Material, USDA Forest Products Laboratory, Revised 2021. Accessed 2026-07-16.
Reviewed 2026-07-16. Planning estimates only; confirm project-specific requirements.