Lumber Sizes ChartHow big is a 2 x 4?  The actual size of a 2 x 4 is about 1.5 by 3.5 inches.  In fact, it might be up to 2/16″ less than that, depending on a some important factors.

Whoa!  That’s crazy!

Now I’ve got to tell this story, just because I never knew and found it interesting.

Here’s Why a 2 X 4 Is Actually 1.5 Inches by 3.5 Inches…

There’s some history involved (most of the time we blame either history or marketing when obvious things are obviously wrong!).

During the 18th and 19th centuries, local sawmills were there to satisfy demand using lumber felled nearby. This lumber was not kiln dried (hence it was green) and it was supplied strictly rough sawn from the mill. As a result, lumber sizes varied considerably from one region (and mill) to the next. The sizes were based on local customers and demand.

There weren’t any standards for grading or sizing lumber until as late as 1895. Nevertheless, 2″ evolved over time as the most common thickness for structural lumber like joists, rafters, and studs while 1″ evolved as the most common thickness for boards.

During the second half of the 19th century, the railroad system made it possible for these mills to broaden their markets. That forced increasing degrees of standardizing as mills tried to accommodate the needs of markets that were further away. In addition, they soon realized it was costlier to ship green lumber than dry lumber because they were shipping the water in the green lumber which made it heavier.

Drying the lumber led to shrinkage, which was the first cause of a 2 x 4 being less than (ahem!) 2 inches by 4 inches. Competition and the demands of consumers led from rough sawn lumber to desire for surface planing the lumber, which (literally) shaved a bit more off that 2 inches by 4 inches. The good news is lumber became easier to handle because it was off a standard size and planed lumber was far less likely to leave splinters in the carpenter’s hands.

Even so, it wasn’t until as late as 1969 (!) that the US Department of Commerce once and for all unified lumber sizes across the country, and that’s how we came to have 2 x 4’s that are 1.5 by 3.5 inches.

But Wait, There’s More

Yeah, I know, kinda like those darned steak knives, right?

Here’s the thing, we’ve got a new page and a new feature in G-Wizard Calculator to help with all this lumber sizing madness.  Yup, there’s now a Lumber Sizes page that’s part of our big new Calculator and Charts Cookbook.  You can go there and get a big chart that tells you the actual size of whatever piece of lumber you’re contemplating (at least based on US standards), but it gets even better.

You see, I added a new Lumber Sizes function to G-Wizard Calculator’s Weights applet.  You did know G-Wizard Calculator has a really fancy app to help you calculate weights and even to estimate material costs, right?  Yup, I developed it to help me estimate raw material costs for jobs and it just sort of grew from there.  It’s got all the standard sizes for standard material shapes.  It’s got a nifty sheet metal gauge reference.  And it’s now got a fancy Lumber Sizes function:

Lumber Sizes Chart and Calcullator

The Lumber Sizes Calculator gives you actual sizes for all standard Nominal Lumber Sizes…


To access the Lumber Sizes, be sure to select a Rectangular Shape first, then the button appears at the lower left…

I’ve had a fair number of G-Wizard users popping up lately with new ideas for reference info.  I find that with G-Wizard, I hardly ever drag out my Machinery’s Handbook any more, which is convenient for me.  It’s very convenient for you too if you pick up a copy of G-Wizard.  There’s a Free 30-Day Trial of G-Wizard if you want to try it out.  Something to be aware of is even if you only buy the 1 year license, you have lifetime access to G-Wizard.  What happens after 1 year is there will be a spindle power limit equal to the number of years you’ve subscribed.  For Hobbyists, that may be all you’d ever need.  For Pros, you can either renew as it expires or just by the lifetime edition and have no subscription.


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How Big is a 2 X 4? Hint: Lumber Sizes are Deceiving and Here’s Why
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