OS Details

Samsung Galaxy J8 has been launched in July 2018.
Samsung Galaxy J8 have Android 8.0 (Oreo)

Screen Dimensions

Samsung Galaxy J8 screen size is 6.0 inch with ~ 75.8% body ratio of actual device size. Physical dimensions for Samsung Galaxy J8 device is 6.27 x 2.98 x 0.32 INCH or ( 159.2 x 75.7 x 8.2 MM).

Displaying of Units are in this order "Height x Width x Thickness"

Screen Pixel Density and CSS Pixel Ratio

"Pixel" is smallest unit/element of any display.

The total number of pixels that fit into an inch is referred to as "Screen Density" or "Pixel Density" and it measured as "Pixels Per Inch".
Pixel Desnsity have limits to display Pixels Per Inch depends on different screen sizes. When number of pixels per inch increases than it's screen-size limit, the Display resolution will increase but actual device width/height in pixels remain same. Actual device pixels are known as Device Independent Pixels or CSS Pixel Ratio.

Samsung Galaxy J8 resolution is 720 x 1480 ^PX with ~ 274 pixel desnsity.
Samsung Galaxy J8 viewport size is 360 x 740 ^PX with ~ 137 actual pixel density, which means it have 2 xhdpi display pixel density.

Screen Resolution and Viewport

The sum of pixels which are displaying on a device is called as "Screen Resolution". and sum of actual pixels of any device is reffered to as "Viewport".

Samsung Galaxy J8 have 6.0" physical screen size and its resolution is about 720 x 1480 Pixels with approximately 274 PPI pixel density. Samsung Galaxy J8 has viewport size 360 x 740 Pixels and its pixel ratio is about 2.

For better understanding screen actual sizes, viewport sizes, display resolution and about their density click here.

CSS Media Queries

Samsung Galaxy J8 Media Queries (In terms of Mobile only)

@media only screen and (min-width: 360px) and (max-width: 767px) { /* Your Styles... */ }

Samsung Galaxy J8 Min-Width Media Queries

@media only screen and (min-width: 360px) { /* Your Styles... */ }

Samsung Galaxy J8 Min-Height Media Queries

@media only screen and (min-height: 740px) { /* Your Styles... */ }

Samsung Galaxy J8 Landscape Media Queries

@media only screen and (min-width: 740px) and (orientation: landscape) { /* Your Styles... */ }

Samsung Galaxy J8 Portrait Media Queries

@media only screen and (min-width: 360px) and (orientation: portrait) { /* Your Styles... */ }

Samsung Galaxy J8 Device Width Media Queries

@media only screen and (min-device-width: 360px) and (orientation: portrait) { /* Your Styles... */ }
@media only screen and (min-device-width: 740px) and (orientation: landscape) { /* Your Styles... */ }

Samsung Galaxy J8 Retina Media Queries

@media
  only screen and (-webkit-min-device-pixel-ratio: 2),
  only screen and (   min--moz-device-pixel-ratio: 2),
  only screen and (     -o-min-device-pixel-ratio: 2/1),
  only screen and (        min-device-pixel-ratio: 2),
  only screen and (                min-resolution: 274dpi),
  only screen and (                min-resolution: 2dppx) { 
    /* Retina styles here */
}
                                

Retina is actually based upon device pixel ratio. Devices mostly have 2x or 3x display so you can use general retina media queries to display high resolution content on all kind of devices. Retina 2x and Retina 3x media queries given below:

Retina 2x Media Query (for all 2x resolution supported devices)

@media
  only screen and (-webkit-min-device-pixel-ratio: 2),
  only screen and (   min--moz-device-pixel-ratio: 2),
  only screen and (     -o-min-device-pixel-ratio: 2/1),
  only screen and (        min-device-pixel-ratio: 2),
  only screen and (                min-resolution: 192dpi),
  only screen and (                min-resolution: 2dppx) { 
    /* Retina styles here */
}
                                

Retina 3x Media Query (for all 3x resolution supported devices)

@media
  only screen and (-webkit-min-device-pixel-ratio: 3),
  only screen and (   min--moz-device-pixel-ratio: 3),
  only screen and (     -o-min-device-pixel-ratio: 3/1),
  only screen and (        min-device-pixel-ratio: 3),
  only screen and (                min-resolution: 384dpi),
  only screen and (                min-resolution: 3dppx) { 
    /* Retina styles here */
}
                                

Samsung Galaxy J8 Specifications

• Launch Date July 2018
• Android 8.0
• Physical Screen Size 6.0 INCH
• Resolution 720 x 1480 PX
• Viewport Size 360 x 740 PX
• Pixel Density 274 PPI
• Device-Independent Pixels 137 PPI
• Pixel Ratio 2 xhdpi
• Width 720 PX
• Height 1480 PX
• Device Width 360 PX
• Device Height 740 PX
• Dimensions 159.2 x 75.7 x 8.2 mm (6.27 x 2.98 x 0.32 in)
• Weight 177 g - 6.24 oz