What size should be the size of A4 Paper?

Question

and I want to make its width and height the same as A4 Page

Can someone tell me which size?

Note: it is not necessary to have the exact width and height!

Answer 1

It depends on the permission:

72 dpi (web) = 595 X 842 pixels 
300 dpi (print) = 2480 X 3508 pixels 
600 dpi (print) = 4960 X 7016 pixels

Answer 2

As you can see here (wikipedia) you will need to do this 210 mm × 297 mm.

Converting millimeters and centimeters to pixels (and vice versa) depends on the DPI of the screen you are using - this is not a constant.

See this as well as the question and answers.

Answer 3

, A4 - 21x29,7 8,3 11,7 .

But, and it's just FYI, when he gets out of his car, you lose a couple of millimeters from each edge, so the most important thing is to make sure that you configure the exit from your post-process software (for example, LightRoom or PhotoShop, etc.), Otherwise, the composition will be screwed.