android - What is the difference between "px", "dip", "dp" and "sp"?

What is the difference between Android units of measure?

• px



• dip


• dp


• sp

Answer

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:

+----------------+----------------+---------------+-------------------------------+
| Density Bucket | Screen Density | Physical Size | Pixel Size                    | 
+----------------+----------------+---------------+-------------------------------+
| ldpi           | 120 dpi        | 0.5 x 0.5 in  | 0.5 in * 120 dpi = 60x60 px   | 

+----------------+----------------+---------------+-------------------------------+
| mdpi           | 160 dpi        | 0.5 x 0.5 in  | 0.5 in * 160 dpi = 80x80 px   | 
+----------------+----------------+---------------+-------------------------------+
| hdpi           | 240 dpi        | 0.5 x 0.5 in  | 0.5 in * 240 dpi = 120x120 px | 
+----------------+----------------+---------------+-------------------------------+
| xhdpi          | 320 dpi        | 0.5 x 0.5 in  | 0.5 in * 320 dpi = 160x160 px | 
+----------------+----------------+---------------+-------------------------------+
| xxhdpi         | 480 dpi        | 0.5 x 0.5 in  | 0.5 in * 480 dpi = 240x240 px | 
+----------------+----------------+---------------+-------------------------------+
| xxxhdpi        | 640 dpi        | 0.5 x 0.5 in  | 0.5 in * 640 dpi = 320x320 px | 

+----------------+----------------+---------------+-------------------------------+

+---------+-------------+---------------+-------------+--------------------+
| Unit    | Description | Units Per     | Density     | Same Physical Size | 
|         |             | Physical Inch | Independent | On Every Screen    | 
+---------+-------------+---------------+-------------+--------------------+
| px      | Pixels      | Varies        | No          | No                 | 
+---------+-------------+---------------+-------------+--------------------+
| in      | Inches      | 1             | Yes         | Yes                | 

+---------+-------------+---------------+-------------+--------------------+
| mm      | Millimeters | 25.4          | Yes         | Yes                | 
+---------+-------------+---------------+-------------+--------------------+
| pt      | Points      | 72            | Yes         | Yes                | 
+---------+-------------+---------------+-------------+--------------------+
| dp      | Density     | ~160          | Yes         | No                 | 
|         | Independent |               |             |                    | 
|         | Pixels      |               |             |                    | 
+---------+-------------+---------------+-------------+--------------------+
| sp      | Scale       | ~160          | Yes         | No                 | 

|         | Independent |               |             |                    | 
|         | Pixels      |               |             |                    | 
+---------+-------------+---------------+-------------+--------------------+

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