How much load can a (wood) 4"x 6" handle with a span of 16' with supports only at the ends. I have a total of 6,200 load pounds on it.

  • 1
    How is the load distributed? Evenly, or all in one place (worst case is the center)? How much deflection is allowed? This is normally the limiting factor.
    – Mattman944
    Oct 16, 2019 at 22:14
  • Snow, wind, seismic, and human loads are live loads (i.e. temporary loads). Is your 6200 lbs. a dead (static) load? Oct 17, 2019 at 1:26

2 Answers 2


There are wood load calculators online available to punch in the numbers: https://awc.org/codes-standards/calculators-software/spancalc That should give you the answer.

  • Did you try the “calculator “? It’s only for repetitive loads (lbs. per square foot) and only goes down to 30 psf.
    – Lee Sam
    Oct 20, 2019 at 13:04
  • I did not try this one but another I could not remember. There are many out there just search Google.
    – Ride Sun
    Oct 20, 2019 at 16:56

It depends on 1) species of wood, 2) grade of wood, 3) duration of load, 4) if used repetitively (like joists).

Typically, for SPF (spruce, pine, fir) with medium grading and permanently loaded, a 4x6 spanning 16’ can support about 1500 lbs. including the weight of the beam.

If it’s for a “short duration” (less than 2 months) you can increase it by 15%. If it’s “very short duration “ (less than 7 days), you can increase it by 25%. If it’s an “impact load” you can double it to about 3000 lbs.

  • What wood species would you recommend to horizontally and permanently support floor joists. We have an addition (built in 1920) with minor sagging. I want to put additional precautionary support.
    – Tonkadog
    Dec 3, 2022 at 13:32

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