Difference between “px”, “dip”, “dp” and “sp”

  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.
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 dpi 0.5 x 0.5 in 0.5 in * 240 dpi = 120×120 px
xxhdpi320 dpi 0.5 x 0.5 in 0.5 in * 320 dpi = 160×160 px
xxhdpi480 dpi 0.5 x 0.5 in 0.5 in * 480 dpi = 240×240 px
xxxhdpi640 dpi 0.5 x 0.5 in 0.5 in * 640 dpi = 320×320 px
UnitDescription Units per physical InchDensity IndependentSame Physical size on every screen
pxPixelsVariesNoNo
inInches1YesYes
mmMillimeters 25.4YesYes
ptPoints 72YesYes
dpDensity Independent Pixels~160YesNo
spScale Independent Pixels~160YesNo

Source : Stackoverflow

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