2x4 would be said: "Two by Four" https://www.thespruce.com/dimensional-lumber-definition-1821735
ell.stackexchange.com/users/115820/bhundven
To add to bhundven's excellent and correct answer, the word "by" is spoken in English in other contexts when the "x" is written.
For instance, you may hear of a 6x6 maze ("six by six maze"), or a 4x4 magic square ("four by four magic square"), or a room measuring 12 feet x 10 feet ("twelve feet by ten feet").
(There's also a class of sport utility vehicle called a 4x4 ["four by four"] because it has four wheels and four-wheel drive.)
ell.stackexchange.com/users/115842/Wastrel
x , Symbol.
5: (used between figures indicating dimensions) by : 3″ × 4″ (read: “three by four inches”); 3″ × 4″ × 5″
(read: “three by four by five inches”). –
https://www.dictionary.com/browse/x See also, display resolution (e.g. 1920 × 1080) Geometric dimension of an object, such as noting that a room is 10 feet × 12 feet in area, where it is usually read as "by" (for example: "10 feet by 12 feet")
The lower-case Latin letter x is sometimes used in place of the multiplication sign.
This is considered incorrect in mathematical writing {because you're supposed to use a Unicode glyph }.
– Multiplication sign
ell.stackexchange.com/users/5117/Mazura
I am a carpenter by trade and you would say 2 by 4 - in the old days the 2x4 would actually be 2" x 4" because they did not plane anything - now they plane the wood to 1 1/2 x 3 1/2 so basically they still hang onto the original size
ell.stackexchange.com/users/115870/Norm
It is pronounced "two by four" or "tuba four" as supercat suggested; I think I say it both ways myself.
@Mazura is correct about the actual size which probably results from the line upon which the saw blade centers, two inches in one direction and four inches in the other.
The blade obviously is wider than the line, which means the actual dimension is less than what is stated.
I agree that is somewhat annoying.
Also, we Americans still surprisingly cling to the English system of measurement, which they have abandoned.
Personally, I prefer metric.
ell.stackexchange.com/users/115847/M. W.
Recently, I found "2x4" as a weapon in a game I played.  I found that it's a common standard for  lumber board .  I tried to pronounce it as "two multiplies four" but it feels really weird.  How should I pronounce this word?
How do you pronounce 2×4 (board)
ell.stackexchange.com
<reading-aloud>
ell.stackexchange.com/questions/248802
ell.stackexchange.com/users/110583/eth4io
 The word "by" is spoken in English in other contexts when the "x" is written. For instance, you may hear of a 6x6 maze ("six by six maze"), or a 4x4 magic square ("four by four magic square"), or a room measuring 12 feet x 10 feet ("twelve feet by ten feet").   There's also a class of sport utility vehicle called a 4x4 ["four by four"] because it has four wheels and four-wheel drive. In this sentence, the "x" stands for "by" but it can also represent the multiplication sign.
In this sentence, the "x" stands for "by" but it can also represent the multiplication sign.