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

Query:

What is the difference between Android units of measure?

  • px
  • dip
  • dp
  • sp

What is the difference between “px”, “dip”, “dp” and “sp”? Answer #1:

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
    Scaleable Pixels OR 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 the user’s preference. Note, the Android documentation is inconsistent on what sp actually stands for, one doc says “scale-independent pixels”, the other says “scaleable pixels”.

From Understanding Density Independence In Android:

Density BucketScreen DensityPhysical SizePixel Size
ldpi120 dpi0.5 x 0.5 in0.5 in * 120 dpi = 60×60 px
mdpi160 dpi0.5 x 0.5 in0.5 in * 160 dpi = 80×80 px
hdpi240 dpi0.5 x 0.5 in0.5 in * 240 dpi = 120×120 px
xhdpi320 dpi0.5 x 0.5 in0.5 in * 320 dpi = 160×160 px
xxhdpi480 dpi0.5 x 0.5 in0.5 in * 480 dpi = 240×240 px
xxxhdpi640 dpi0.5 x 0.5 in0.5 in * 640 dpi = 320×320 px
UnitDescriptionUnits Per Physical InchDensity Independent?Same Physical Size On Every Screen?
pxPixelsVariesNoNo
inInches1YesYes
mmMillimeters25.4YesYes
ptPoints72YesYes
dpDensity Independent Pixels~160YesNo
spScale Independent Pixels~160YesNo

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

Answer #2:

Pretty much everything about this and how to achieve the best support for multiple screens of different sizes and densities is very well documented here:

  • Supporting Multiple Screens

Screen size
Actual physical size, measured as the screen’s diagonal. For simplicity, Android groups all actual screen sizes into four generalized sizes: small, normal, large, and extra-large.

Screen density
The number of pixels within a physical area of the screen; usually referred to as dpi (dots per inch). For example, a “low” density screen has fewer pixels within a given physical area, compared to a “normal” or “high” density screen. For simplicity, Android groups all actual screen densities into six generalized densities: low, medium, high, extra-high, extra-extra-high, and extra-extra-extra-high.

Orientation
The orientation of the screen from the user’s point of view. This is either landscape or portrait, meaning that the screen’s aspect ratio is either wide or tall, respectively. Be aware that not only do different devices operate in different orientations by default, but the orientation can change at runtime when the user rotates the device.

Resolution
The total number of physical pixels on a screen. When adding support for multiple screens, applications do not work directly with resolution; applications should be concerned only with screen size and density, as specified by the generalized size and density groups.

Density-independent pixel (dp)
A virtual pixel unit that you should use when defining UI layout, to express layout dimensions or position in a density-independent way. The density-independent pixel is equivalent to one physical pixel on a 160 dpi screen, which is the baseline density assumed by the system for a “medium” density screen. At runtime, the system transparently handles any scaling of the dp units, as necessary, based on the actual density of the screen in use. The conversion of dp units to screen pixels is simple: px = dp * (dpi / 160). For example, on a 240 dpi screen, 1 dp equals 1.5 physical pixels. You should always use dp units when defining your application’s UI, to ensure proper display of your UI on screens with different densities.

If you are at all serious about developing an Android app for more than one type of device, you should have read the screens support development document at least once. In addition to that, it is always a good thing to know the actual number of active devices that have a particular screen configuration.

Difference between “px”, “dip”, “dp” and “sp”-Answer #3:

I will elaborate more on how exactly does dp convert to px:

  • If running on an mdpi device, a 150 x 150 px image will take up 150 * 150 dp of screen space.
  • If running on an hdpi device, a 150 x 150 px image will take up 100 * 100 dp of screen space.
  • If running on an xhdpi device, a 150x150 px image will take up 75 * 75 dp of screen space.

The other way around: say, you want to add an image to your application and you need it to fill a 100 * 100 dp control. You’ll need to create different size images for supported screen sizes:

  • 100 * 100 px image for mdpi
  • 150 * 150 px image for hdpi
  • 200 * 200 px image for xhdpi

Answer #4:

px – Pixels – point per scale corresponds to actual pixels on the screen.

i – Inches – based on the physical size of the screen.

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

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

dp – 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.

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

Take the example of two screens that are the same size but one has a screen density of 160 dpi (dots per inch, i.e. pixels per inch) and the other is 240 dpi.

                          Lower resolution screen     Higher resolution, same size
Physical Width                      1.5 inches                        1.5 inches
Dots Per Inch (“dpi”)               160                               240
Pixels (=width*dpi)                 240                               360
Density (factor of baseline 160)    1.0                               1.5

Density-independent pixels          240                               240
(“dip” or “dp” or “dps”)

Scale-independent pixels 
 (“sip” or “sp”)                  Depends on user font size settings    same

Answer #6:

Definitions

px or dot is a pixel on the physical screen.

dpi are pixels per inch on the physical screen and represent the density of the display.

Android gives alias names to several densities

  • ldpi (low) ~120dpi
  • mdpi (medium) ~160dpi
  • hdpi (high) ~240dpi
    • most devices in 2015 are here
  • xhdpi (extra-high) ~320dpi
    • Apple iPhone 4/5/6, Nexus 4
  • xxhdpi (extra-extra-high) ~480dpi
    • Nexus 5
  • xxxhdpi (extra-extra-extra-high) ~640dpi

dip or dp are density-indenpendant pixels, i.e. they correspond to more or less pixels depending on the physical density.

  • 1dp = 1px on mdpi
enter image description here

sp or sip is a scale-independant pixel. They are scaled when the Large Text option is turned on in Settings > Accessibility

  • 1sp = 1dp
  • 1sp = 1.2dp with accessibility Large Text

What to use?

Use sp for Text size.

Use dp for everything else.

Answer #7:

Where to use what & relationship between px & dp?

Density-independent pixel (dp)

A virtual pixel unit that you should use when defining UI layout, to express layout dimensions or position in a density-independent way. As described above, the density-independent pixel is equivalent to one physical pixel on a 160 dpi screen, which is the baseline density assumed by the system for a “medium” density screen. At runtime, the system transparently handles any scaling of the dp units, as necessary, based on the actual density of the screen in use. The conversion of dp units to screen pixels is simple:

px = dp * (dpi / 160).

For example, on a 240 dpi screen, 1 dp equals 1.5 physical pixels. You should always use dp units when defining your application’s UI, to ensure proper display of your UI on screens with different densities.

Understanding pixel to dp and vice versa is very essential (especially for giving exact dp values to creative team)

dp = px * 160 / dpi

MDPI = 160 dpi || Therefore, on MDPI 1 px = 1 dp
For example, if you want to convert 20 pixel to dp, use the above formula,
dp = 20 * 160 / 160 = 20.
So, 20 pixel = 20 dp.

HDPI = 240 dpi - So, on HDPI 1.5 px = 1 dp
XHDPI = 320 dpi - So, on XHDPI 2 px = 1 dp
XXHDPI = 480 dpi - So, on XXHDPI 3 px = 1 dp

For example, let us consider Nexus 4.
If 24 pixels to be converted to dp and if it is a Nexus 4 screen, developers can
convert it to dp easily by the following calculation :
dp = 24 * 160 / 320 = 12 dp
Screen dimension:
768 x 1280 pixel resolution (320 ppi or 320dpi)
Optional (screen size):
 4.7" diagonal
  • Try to get all pixel values in even numbers from the creative team. Otherwise precision lose will happen while multiplying with 0.5.

px

It is explained above. Try to avoid in layout files. But there are some cases, where px is required. for example, ListView divider line. px is better here for giving a one-pixel line as a divider for all across screen resolutions.

sp

Use sp for font sizes. Then only the font inside the application will change while device fonts size changes (that is, Display -> Fonts on Device). If you want to keep a static sized font inside the app, you can give the font dimension in dp. In such a case, it will never change. Developers may get such a requirement for some specific screens, for that, developers can use dp instead of sp. In all other cases, sp is recommended.

Hope you learned something from this post.

Follow Programming Articles for more!

About ᴾᴿᴼᵍʳᵃᵐᵐᵉʳ

Linux and Python enthusiast, in love with open source since 2014, Writer at programming-articles.com, India.

View all posts by ᴾᴿᴼᵍʳᵃᵐᵐᵉʳ →