I would like to print a Polaroid like image that is 336x407 mm big. What size is that in pixel and what PPI should I use?

  • 3
    the size in pixel depends on the resolution you want to print with, the higher the resolution, the more pixel you get. e.g. for 300 pixel per inch you get 3969x 4807px as a result.
    – KMSTR
    Commented Nov 28, 2013 at 17:16
  • Pixels have no size so really... you can't directly translate a mm to a pixel.
    – Scott
    Commented Dec 16, 2013 at 17:51

2 Answers 2


You have to know the pixels in order to get the pixels-per-inch conversion. For example, if you have a 100x100px image that you wanted to print as 1x1in, you would print at 100ppi. You don't have enough information to translate from measurements to pixels.


A pixel does not have a size until it is converted into a physical form by printing it on paper, displaying it on a screen at a specific resolution, or making it into a card for spectators to hold up at a football game, for example.

The most important thing to know about pixels in digital imaging is that a pixels is simply a "spot." It is generally (but not always) square. And it is always one solid color. It is one discrete piece of digital color information, nothing more. A pixel has no size.

A millimeter is a physical size that does not change.

  • >> " ... or making it into a card for spectators to hold up at a football game, for example." Loved it. Thanks! Commented Apr 17, 2017 at 19:06
  • Glad to hear! I keep trying to use that example, so people see that pixels can make pictures in any size -- including stadium-sized.
    – user8356
    Commented Apr 18, 2017 at 18:53

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