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I want to know how to measure wood and understand what means for exampe (( 4x4 or 7x3 ))? Answered



This might be a slightly positive note: most plans (e.g. magazines, pre-printed etc. etc.) account for the fact that a "2 x 4" doesn't really measure exactly 2 inches thick x 4 inches wide.....if that's any comfort to you!

4 x 4 means 4 inches thick 4 inches deep, likewise 7x 3 is 7 inches thick, 4 inches deep.

An inch is 25.4 mm.

EVEN PLANED WOOD IS SIZED LIKE THAT. So a 4 x4 PAR (planed all round ) ends up usually about 3.75 x 3.75.


Hi, Steve. In the U.S., that's called "finished lumber," and we actually lose much more than you'd expect. A finished 2x4 is actually closer to 1-3/8 x 3-3/8 (as I discovered when I dimensioned and cut for a small project without measuring the real wood first; sigh...).

It's DAR down here. Dressed All Round.

Yes, it comes as a NASTY shock ! But it looks like less nasty shock here than there....I bet with modern saws, the loss is actually a lot smaller than they say, but they can get away with more cuts from the same log

Now I've got my own planer/thicknesser, I resaw my own lumber, but its a bit of a bugger to do.


The forest-products industry claims the difference is due to the difference between wet and dry wood, and that a 2x4 is equivalent to what would have been 2x4 if it had just come out of the tree. Nobody believes that one.

They also claim that a modern 2x4 is as strong as the "real" 2x4's of the past, when used for framing and so on. Given changes in how lumber is harvested and processed -- and given actual serious research done by folks like the University of Wisconson's materials science labs, which have done a LOT of research into everything from raw wood to wood laminates (the laminated wood I-beam is one of their ideas) -- I'm almost willing to believe that.

(My own late-19th-century house is built with lumber rough-milled to "real" inch dimensions. But since it was originally intended to be cheap employee housing, they used 1x3's rather than 1x4's. Given the additional fractional inch that's *probably* close to equivalent, but it's going to be a pain if I ever want to install an in-wall cabinet.)

Depends on the finish - Sawn wood will be as stated 4x4 6 x 8 etc but rough direct from the saw.

Finished timber will be that less the planed off surface to make it smooth. generally th difference isn't enough to make a big construction difference BUT always order over size and cut to what you want or design from what you have.

Most sheet material you are likely to fond will be in 8 x 4 foot sheets.

i also cut and plane my own timber mainly because I use a lot of reclaimed stuff and size is very variable.

As an addition wood is sold in 2 ways either by cubic volume i.e. so much per cubic foot (or meter)


By linear length - i.e. for a given section so much per foot length - this changes according to the cross section.

Websearch for "lumber dimensions" will find details, but basically you just have to know that, for example, a standard "eight foot two-by-four" is a rectangular solid roughly 8 feet long by 1.5 inches by 3.5 inches. Length is always in inches; width and thickness are "nominal" values. When you start actually constructing things, you work with real inches, and you just have to remember to do the conversions and/or measure as you go..

Plywood and other "sheet goods" are measured in real inches... mostly. Their thickness is often a bit under the nominal size. If that dimension matters to you, you have to measure them to know what you've got.

If you're buying something fancier than construction-quality lumber or sheet goods, it is less likely to come in these standard sizes, since it's assumed you're going to be machining it to its final size anyway and since they (and you) don't want to waste any wood that might be useful. These woods will generally be sold as boards cut to a "rough" thickness (measured in real inches, but that may not be exact)) and having random widths (whatever they could get out of the tree) also measured in inches.