Because the size of paper varies depending on the Pixels Per Inch of the setting in Photoshop, there is no defined size for A4 paper in Photoshop or MS Paint. Instead, The table below displays the dimensions of A4 paper in pixels at different Pixels Per Inch (PPI or Dots Per Inch). Each pixel count is in 8 bits of colour. You can change the color mode in Photoshop when creating a new project.
| Paper Size Type | Paper Width | Paper Height |
| A4 Dimensions @ 72 DPI | 595 Pixels | 842 Pixels |
| A4 Dimensions @ 200 DPI | 1654 Pixels | 2339 Pixels |
| A4 Dimensions @ 300 DPI | 2480 Pixels | 3508 Pixels |
| A4 Dimensions @ 400 DPI | 3307 Pixels | 4677 Pixels |
| A4 Dimensions @ 600 DPI | 4961 Pixels | 7016 Pixels |
| A4 Dimensions @ 1200 DPI | 9921 Pixels | 14031 Pixels |
| Letter Size @ 72 DPI | 612 Pixels | 792 Pixels |
| Letter Size @ 200 DPI | 1700 Pixels | 2200 Pixels |
| Letter Size @ 300 DPI | 2550 Pixels | 3300 Pixels |
| Letter Size @ 400 DPI | 3400 Pixels | 4400 Pixels |
| Letter Size @ 600 DPI | 5100 Pixels | 6600 Pixels |
| Letter Size @ 1200 DPI | 10200 Pixels | 13200 Pixels |
Letter size: Canada and the United States of America.
A4 size in mm: United Kingdom, Australia, Germany, Singapore, India, United Arab Emirates, Philippines, New Zealand and nearly ever other country in the world.
What are Pixels?
Pixels are not used for measuring size.
One pixel is a small dot of illumination on a display screen.
Multiple pixel dots compose an image. This is why Dots Per Inch or Pixels Per Inch is used as a standard.
Pixels are most standardised as 8bit in colour in 24bit displays. Each pixel can achieve over 16 million colours in this case.
How many Pixels of Bleed for Photoshop?
Adding a bleed to Photoshop is as easy as increasing how many pixels surround the space you want to work with. The area surrounding your workspace in Photoshop should always have a bleed of at least 3 millimeters to adjust for printing errors with it goes on paper. But we, and many others, recommend 5 millimeters to adjust for a wider variety of printers.