# two-by-fours **URL:** \ **Category:** Factual Questions\ **Created:** [May 9, 2001, 1:10pm UTC](https://boards.straightdope.com/t/two-by-fours/64861 "2001-05-09T13:10:19Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![cvrice](https://avatars.discourse-cdn.com/v4/letter/c/7feea3/32.png) [@cvrice](https://boards.straightdope.com/u/cvrice)\ **Post date:** [May 9, 2001, 1:10pm UTC](https://boards.straightdope.com/t/two-by-fours/64861/1 "2001-05-09T13:10:19Z")
Why are two-by-fours at the lumber yard actually 1 1/2 by 3 1/2 inches? Could be: 1. the saw blade is really big (1/2 inch wide) 2. they used to be 2x4 inches, but were made smaller to use less wood, make more $$$$, but the name stayed the same 3. a scheme by men to convince you that their wood is bigger than it actually is ---
**Author:** ![Spritle](https://avatars.discourse-cdn.com/v4/letter/s/5daacb/32.png) [@Spritle](https://boards.straightdope.com/u/Spritle)\ **Post date:** [May 9, 2001, 1:23pm UTC](https://boards.straightdope.com/t/two-by-fours/64861/2 "2001-05-09T13:23:57Z")
It’s not exactly 1 1/2 by 3 1/2, however, you are right that it’s not 2" x 4". add in the thickness of drywall… ---
**Author:** ![Scarlett67](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scarlett67/32/7387_2.png) [@Scarlett67](https://boards.straightdope.com/u/Scarlett67)\ **Post date:** [May 9, 2001, 1:25pm UTC](https://boards.straightdope.com/t/two-by-fours/64861/3 "2001-05-09T13:25:32Z")
According to Mr. Scarlett, the amateur carpenter, “rough-cut” 2x4s (such as were used in the walls of our house) are actually 2x4. The size reduction comes when they’re planed smooth. Mr. S gives the analogy of a “quarter-pound” hamburger – the weight is before cooking, not after. Why the system was set up that way, he doesn’t know. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [May 9, 2001, 1:29pm UTC](https://boards.straightdope.com/t/two-by-fours/64861/4 "2001-05-09T13:29:14Z")
Yeah, it has to do with the size before it’s smoothed out. You lose about half an inch during the planing. four-by-fours are about 3.5x3.5 inches, for example. ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [May 9, 2001, 7:06pm UTC](https://boards.straightdope.com/t/two-by-fours/64861/5 "2001-05-09T19:06:13Z")
**cvrice** , welcome to the SDMB! **Scarlett67** and **friedo** are right. The dimension is the rough cut dimension of the wet wood. In the words of [Louisiana-Pacific](http://www.lpcorp.com/products/p_faqs.jsp): > [@](#): > > How come a 2x4 measures out to be 1 ½" x 3 ½"? > > Lumber is usually referred to by its nominal size rather than its actual size. A piece of lumber is 2" thick and 4" wide when it is cut at the sawmill. Lumber shrinks lightly in the drying process and it is reduced further being planed from rough saw cut surface to smooth finish. ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [May 9, 2001, 8:16pm UTC](https://boards.straightdope.com/t/two-by-fours/64861/6 "2001-05-09T20:16:35Z")
IIRC, the size of a 2 x 4 has shrunk over the years (I believe it used to be 1 3/4 x 3 3/4). It was never exactly 2 x 4 due to the explanations already given, but lumber manufacturers reduced the size further in order to get a few more boards out of a log. ---
**Author:** ![TBone2](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@TBone2](https://boards.straightdope.com/u/TBone2)\ **Post date:** [May 9, 2001, 11:08pm UTC](https://boards.straightdope.com/t/two-by-fours/64861/7 "2001-05-09T23:08:42Z")
I worked for years as a builder of houses, and I’ve done a lot of work in houses that were older and were framed with rough-sawn 2x4’s that actually _were_ 2" by 4", or pretty close. The story I heard many times as to why the lumber is planed nowadays makes a lot of sense if you’ve ever had to handle rough-cut lumber. OUCH! Carpenters got pretty sick of picking dozens of splinters out of their hands and other body parts every day, and their complaints got back to the sawmill owners, who detected a market opportunity to sell nicely planed boards at a considerably higher price. Any carpenter will tell you two things – rough-sawn lumber is hard on the hands and requires gloves for safety, and gloved hands just can’t pick a nail from a nail pouch. Note also that the corners of framing lumber are somewhat rounded for the same reason – to avoid splinters. ---
**Author:** ![thinksnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thinksnow/32/2849_2.png) [@thinksnow](https://boards.straightdope.com/u/thinksnow)\ **Post date:** [May 9, 2001, 11:13pm UTC](https://boards.straightdope.com/t/two-by-fours/64861/8 "2001-05-09T23:13:10Z")
You can, however, find true 2x4 boards. Not really practical for most people, but for woodworkers, it might be something worth looking into. We’ve got a few true 2x4s, course, they’re also oak, which is something you don’t normally find, either. ---
**Author:** ![loislane138](https://avatars.discourse-cdn.com/v4/letter/l/f19dbf/32.png) [@loislane138](https://boards.straightdope.com/u/loislane138)\ **Post date:** [May 10, 2001, 2:14am UTC](https://boards.straightdope.com/t/two-by-fours/64861/9 "2001-05-10T02:14:33Z")
In my theatre scene shop class, the teachers told us that 2x4’s were actuall 1 3/4 x 3 3/4, a 1/4 inch less than what its supposed to be. Also, when you get to larger sizes of lumber, the sizes start to decrease by 1/2 inch. They said it had something to do with the sanding down of rough lumber.