What is the difference between “px”, “dip”, “dp” and “sp”?

What is the difference between the following?

  • px
  • dip
  • dp
  • sp

From the Android Developer Documentation:

  1. px
    Pixels – corresponds to actual pixels on the screen.

  2. in
    Inches – based on the physical size of the screen.
    1 Inch = 2.54 centimeters

  3. mm
    Millimeters – based on the physical size of the screen.

  4. pt
    Points – 1/72 of an inch based on the physical size of the screen.

  5. dp or dip
    Density-independent Pixels – an abstract unit that is based on the physical density of the screen. These units are relative to a 160
    dpi screen, so one dp is one pixel on a 160 dpi screen. The ratio of
    dp-to-pixel will change with the screen density, but not necessarily
    in direct proportion. Note: The compiler accepts both “dip” and
    “dp”, though “dp” is more consistent with “sp”.

  6. sp
    Scale-independent Pixels – this is like the dp unit, but it is also scaled by the user’s font size preference. It is recommended you
    use this unit when specifying font sizes, so they will be adjusted
    for both the screen density and user’s preference.

From Understanding Density Independence In Android:

More info can be also be found in the Google Design Documentation.

To calculate dimensions on real device this app can be used.