Render size messes up my image

im getting somekinda problem when i try to render my scene. okay normally when i render stuff i just use the default size but this time i want it to be bigger say 1200 by 1600 or something instead of 600 by 800. but when i increase the image size all the edges dont look as sharp and get kinda pixelated how do i fix this. thanks

They don’t actually look that way. Blender just resizes the window so that the vertical number of pixels is the same size as your monitor, and it doesn’t re-anti-alias it in that process, so it looks choppy. Once you export the image it will look just the same as others.

awesome thanks!