What size should passport photo be?

Question

can you tell me in pixels, if possible.

Answer 1

Pixels would be meaningless.  It's the measurement that matters, since you have to provide a physical photo.  

From the State Department website:

Your photographs must be:

    * 2x2 inches in size

    * Identical

    * Taken within the past 6 months, showing current appearance

    * Color

    * Full face, front view with a plain white or off-white background

    * Between 1 inch and 1 3/8 inches from the bottom of the chin to the top of the head

    * Taken in normal street attire