The required resolution for an A4-sized image is 2480 x 3508 pixels at 300 ppi (pixels per inch) . However, the number of pixels can vary depending on the resolution of the image. For example, an A4 size in pixels with a resolution of 72 PPI is 595 x 842 pixels, while an A4 size in pixels with a resolution of 300 PPI is 2480 x 3508 pixels. The table below shows the dimensions of A4 paper size in pixels at different resolutions:

Its important to note that in theory, an A4 size can be displayed or printed in any resolution, but a minimum number of pixels is required for a sharp image. The minimum number of pixels for a sharp image is 300 PPI/DPI.