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By Chris | February 15, 2008 - 5:15 pm - Posted in Specs & Data, Treated Wood

Basic lumber dimensions are not as basic to many people as you might think they are. I get asked about actual lumber dimensions on a regular basis. Most people know that a 2×4 is actually 1.5″x3.5″ but the measurements get a little hazy with the large boards like 2×8’s and 2×12’s.

Lumber Dimensions

Here is a simple chart to clear up the confusion about 1x, 2x, and 4x nominal lumber dimensions versus actual lumber dimensions. The chart also includes the equivalent metric lumber dimensions. This chart applies to treated and untreated pine construction grade lumber.

lumber dimensions chart

This chart applies to the lumber dimensions of “quarter” measurements. The nominal dimensions are said as “five-quarter by four” or “six-quarter by six” etc. These are not all that common but you can usually find “five-quarter” decking whose actual dimension is 1″x5.5″.

five quarter lumber dimensions

Timber Dimensions

Lumber cut 5 inches or thicker is generally classified as timbers. Timbers are usually cut “rough” to actual dimensions. In other words, what you see is what you get. A 6×6 is 6″x6″, a 10×10 is 10″x10″ and so forth.

Post Dimensions

Round stock dimensions can get a little complicated but we will keep it simple here. A thorough discussion including large poles requires getting into the differences between poles and pilings and classes of utility poles and what you are using them for and it goes on and on so…so for the purpose of this article, I will stick to small posts.

Small posts are usually measured by the top size (the little end). So, if you want a 4″ top x 8′ long fence post, you would ask for a “four inch – eight” post. The line between posts and poles is a fuzzy one but after about ten or twelve feet long, whatever it is that you want usually become a pole. If you are using it in water to support a structure it is probably a piling, which is used upside down and measured by the butt (the big end)… and see how it easy it is to get complicated when discussing poles?

If you want square posts make sure you are clear about that when you ask for “posts”.

Lumber Dimensions Questions?

If you have any questions about lumber dimensions, let me know with a comment. I am always happy to help.


  1. February 26, 2008 @ 4:16 pm

    what would be the nominal size of 8×8, I am building on the river and the company doing the no-rise certoficate asked “what is the nominal size of the timber piles for the dock and the house we are using 8×8 on the house and the dock except for tthe two pieces hold the floating dock what does he mean?

    Posted by Marvin Mintz
  2. February 26, 2008 @ 10:15 pm


    I am not sure they asked you the right question but big timbers like 8×8’s usually come in full-rough dimensions.

    So, an 8×8 is usually actually 8″ by 8″. It is the milling process that makes the actual dimensions of a board smaller but big timbers typically retain their full size.

    However, if you are using S4S (smooth 4 sides) and the timbers were planed, they are probably something more like 7.5″ by 7.5″.

    Thanks for visiting Lumber Talk!


    Posted by Chris
  3. October 6, 2008 @ 9:11 pm

    […] the more common term is “lumber dimensions“, which I have written about before, but people often ask about “lumber sizes” so […]

  4. November 26, 2008 @ 7:03 am

    How difficult is it to obtain timber columns in the range of 12″x18″ and 12″x12″? Are these sizes readily available or would it be less expensive to specify glulam timbers?

    Posted by Karl
  5. November 26, 2008 @ 7:54 am


    12×12’s are easy. 12×18’s are available but more difficult.

    If you are in the south and need just a few, call American Pole and Timber ( If you are in the NE, call For-tek, whose site I cannot remember. In the NW, call (?). If you need large quantities, American Pole and Timber can ship anywhere.

    The price difference between natural wood and glulam depends on the lengths you need. Large timbers increase in price VERY quickly as their length increases because the size of the tree required gets HUGE. For instance, to make a 12×18-20′ timber, you would need a tree with a diameter of about 30″ at the BOTTOM. They just don’t many of those anymore.

    Cost-wise, stick with 12×12 if possible.

    Posted by Chris
  6. January 4, 2009 @ 8:04 pm


    I’m trying to find some replacement posts for my front porch that were damaged in Hurricane Ike. The entire porch, including decorative elements and upper structure seem to be cut from the same size lumber. I can’t tell the type of wood because it is painted and frankly I’m not too knowledgable about wood types anyway. The posts are rectangular with dimensions (actual) of 4 1/4″ x 5 3/4″ and about 8′ 6″ in length. The finish is semi-rough on the small faces and circular saw blade finish on the large faces. The house dates to the early ’60s. Any chance this sounds like a stock product or am I looking at a custon job if I want to match it.



    Posted by Marc
  7. January 10, 2009 @ 8:25 am


    Those are custom sizes but they don’t have to be expensive in the Houston/Galveston area.

    Call the guys at at (713) 434-8008. They will be able to to cut the pieces you need (give them exact measurements). They will probably cut them to even lengths of 8 or 10 feet so you can cut the exact lengths you need.


    Posted by Chris
  8. February 5, 2009 @ 3:47 pm

    Hello Chris. I am in need of copper naphthenate treated 4x6s in eastern Pennsylvania. Could you suggest any sources? Thanks

    Posted by Jack Neary
  9. February 8, 2009 @ 10:15 pm


    Oooh, that’s a tough one. I don’t know of anyone up there but what often works is to contact someone close to there (relatively close, anyway) like the guys at Wheeler in MN and ask them. Sorry I cannot do more.

    What are you building? Is Cu Nap required by the specs?


    Posted by Chris
  10. February 12, 2009 @ 2:36 pm

    Just found your site.We use a little rough cut mostly for decking on trailers.It can be very diffcult to find but in Maryland I use P T Omally in Baltimore or GE Frisco in Upper Marlboro.I find that I must ask whoever is requesting the wood to give me the actual demensions.It nice to know there is someone out there that can help.Its not like going to Home Depot.

    Posted by paul boeckmann
  11. April 25, 2009 @ 5:48 pm

    i would like to know how many cord of wood is in 1000 bf of logs (ya know @ the mill using the log scale stick


    Posted by joe shaw
  12. April 28, 2009 @ 3:10 pm


    Good question. Why on earth do you need to know that? Either way, 1000 bdft = .65 of a cord (65% of a full cord).

    A cord of wood is a stack of wood 48″ wide X 4′ tall X 8′ long. A full cord would have 1,536 bdft.

    Take care,


    Posted by Chris
  13. July 8, 2009 @ 10:40 am

    I seem to remember a change in lumber dimensions in the late 60’s or early 70’s. It seems to me that a 2×4 usedto be 1 3/4 x 3 3/4. Other people think I’m crazy, but I swear I remember trying to match up new lumber with older lumber and having all kinds of trouble. In my memory the change was connected with conservation and high lumber prices. Did I dream it?


    Posted by Ken
  14. July 9, 2009 @ 1:16 pm


    I don’t know of a time when there was a standard of 1 3/4 x 3 3/4. Sometime around the 40’s or 50’s 2x was standardized to 1 1/2 x 3 1/2. However, before that, there was little standardization and the variance in board thicknesses was all over the place.

    You might be thinking of 1x lumber which is 3/4 or you might be thinking of a time when you were trying to match existing lumber in an old structure made with 1 3/4 x 3 3/4′ lumber.

    I DID run across a 1914 grade standard for hemlock that was 1 3/4 x 3 3/4 but that’s a long shot from the 60’s and 70’s.

    …or you could have dreamed it. 🙂

    Take care,


    Posted by Chris
  15. December 12, 2009 @ 10:08 pm

    Yes I think Ken is right. I seem to remember when a 2 X 4 was 1 3/4 in. x 3 3/4 in. That was in the late 60’s.

    Posted by Randy
  16. January 17, 2012 @ 10:28 am

    Chris, when did these measurements for lumber become the industry standard in the US? I’m trying to determine when something was built with modern 2 x 4’s (in Pittsburgh, PA).

    Posted by Michael Marks
  17. October 17, 2012 @ 10:27 pm

    Hi Michael, I bet the answer to your question is somewhere in here: I will try to do a post about that sometime, too. Thanks!

    Posted by Chris

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