If I see a good size that I want, lets say someone's picture says 1200x2400. Does that mean that if I opened up Photoshop and made those exact dimensions for my picture, it would come out the same size as the persons picture who I saw?

If you're an artist, yes. Otherwise, don't resize images before uploading them here. Someone will just upload the proper image and the resized one will be deleted.

https://e621.net/post/show/151950/bdsm-collar-comics-donkey-donkey_transformation-eq

This says 1024x1374 but there is no way this picture is only 350 pixels, inches or any increment of measurement longer than it is wide, it's physically impossible. How does the measuring work?

tony311 said:
If you're an artist, yes. Otherwise, don't resize images before uploading them here. Someone will just upload the proper image and the resized one will be deleted.

No, I don't mean "resize it" I mean make it that size from the very begining, like start off with a page 1024x1374 before I even start drawing and draw the picture based on that size.

xXxSnowLeopardxXx said:
https://e621.net/post/show/151950/bdsm-collar-comics-donkey-donkey_transformation-eq

This says 1024x1374 but there is no way this picture is only 350 pixels, inches or any increment of measurement longer than it is wide, it's physically impossible. How does the measuring work?

The dimensions are correct. It's just an optical illusion that it looks taller. Or your monitor is messed up.