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Lumber numbers?

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  • Lumber numbers?

    What do these numbers mean when buying 'raw' lumber:


    And how do you calculate Board feet?

  • #2
    The numbers you show refer to the thickness. 4/4 = 1 inch. 6/4 = 1 1/2 inches. 8/4 = 2 inches. As in four quarters is 1 inch. Six quarters is 1 1/2 inches and so on.

    To calculate board feet the formula is :

    Width in inches x Length in feet x Thickness in inches


    Width in inches x Length in inches x Thickness in inches


    • #3

      Thank you!!!! Now what's the history of this method... and why don't we just call it 1 inch/ 11/2...etc?


      • #4
        Grizz- if they did it simple then everyone would be smart- this way they have a language of their own --such as cb lingo - woodworkers lingo -kids lingo -- just a guess but a fair one


        • #5
          I think it is because lumber thickness is always expressed in "rough" dimensions. In other words a 1 inch deck board was actually 1 1/4 inch thick from the saw mill prior to being planed to its final thickness of 1 inch, thus it's called 5/4 lumber or "five quarter". Four quarter or 4/4 is actually finished to a nominal 3/4 inch thickness. Don't know the history behind it. That's just how it's always been.
          Last edited by Neal Moore; 04-07-2006, 10:57 AM.
          If it don't fit, don't force it....get a bigger hammer!!


          • #6
            Rampant Speculation

            Maybe because if I wrote 11/4 you might not know if it was 1.25 inches thick or if it was 2.75 inches thick. By always having it as a single fraction (non-reduced) it removes ambiguity. I wouldn't doubt it if they eventually switch to a single number (e.g. 2.5, 5) which reflects the metric cm.
            Sawdust King

            If there is one thing I can make perfect every time it is sawdust.


            • #7
              This made me curious and I did some digging around and came up with a couple of things...

              One is that there are taxes and duties that are based on the amount of wood and in some of the regs it says that the dimensions must be within 1/4"

              But the other reason I found makes more sense. It's easy to do board feet in your head with almost any common width if the thickness is in fourths (easy to calculat the number of linear feet per board foot or visa versa).


              • #8
                Dont know why it is measured that way or why it continues, but finish carpenders all know if you buy a 5/4 x 6" stock for doorframes you always get 1-1/4 x 6 finished measure they cant be fooling around with filler strips & shims and such and keep their work looking right. or stay in business long...

                i always thought it indicated to the miller a 2x4 could be roughly cut to 2x4 then milled, 1 - 1/2 x 3-1/2, that verys with different mills.
                while measurement in quarters meant finished dimention... with no variation,full measure...
                Dremel 1680 & Delta ss250 shopmaster


                • #9
                  I appreciate everybodies input! I've just been a little confused by it all. I've been considering a new/bigger/better bandsaw and a drumsander. I'm finding that purchasing rough/raw lumber and cutting my own boards down to size would be much more, can I afford the tools.

                  I did a search and found these board feet calculators... how cool is these!


                  • #10
                    Just to add a little to the 1/4 measurements for thicknesses. This actually came from sawyers, circular sawyers kerfs were approximately 1/4". When telling the operator how thick to cut logs, the person would hold up 4 fingers to indicate 4/4 thickness, 1 finger for 5/4, 2 fingers for 6/4, etc. Also note that only 1" and thicker woods are permitted to be expressed in this measurement.
                    The National Hardwood Lumber Association has published rules for the Measurement and Inspection of hardwood and cypress effective January 1, 2003. It indicates that the standard thicknesses for lumber are 3/8", 1/2", 5/8", 3/4", 1", 1 1/4", 1 1/2", 1 3/4", 2", 2 1/2", 3", 3 1/2", 4", 4 1/2", 5", 5 1/2", and 6". For surfaced lumber (S2S), you can calculate the standard thickness by subtracting 3/16" for lumber up to 1 1/2" thick and subtracting 1/4" for lumber between 1 3/4" and 4".
                    Something to keep in mind when buying rough lumber. In the rough state, lumber will measure slightly thicker than its nomenclature indicates. For example, 4/4 is actually going to measure typically around 1 1/8". In Thomp's example, the 5/4 wood would measure approximately 1 1/16 when surfaced.
                    Confused yet? If not, you can find all 166 pages of the rules online, just do a search for NHLA Rules for the Inspection & Measurement of Hardwood & Cypress. 5/4 will virtually never measure 1 1/4" once surfaced.

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                    • #11
                      This reminds me of the four carpenters that created a brass band, They call themselves the Tuba Fours
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