OS Details

MacBook 2015 (12 Inch) has been launched in Early 2015.
MacBook 2015 (12 Inch) have macOS Sierra

Device Size

MacBook 2015 screen size is 12 inch screen . Physical dimensions for MacBook 2015 (12 Inch) device is 0.14 x 11.04 INCH or ( 0.35 x 28.05 MM).

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

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.

MacBook 2015 (12 Inch) resolution is 2304 x 1440 ^PX with ~ 226 pixel desnsity.
MacBook 2015 (12 Inch) viewport size is 1280 x 800 ^PX with ~ 113 actual pixel density, which means it have 2.0 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".

MacBook 2015 (12 Inch) have 12" physical screen size with IPS technology and it's native resolution is 2304 x 1440 Pixels with approximately 226 PPI pixel density. MacBook 2015 (12 Inch) has viewport size 1280 x 800 Pixels and its pixel ratio is about 2.0. However MacBook 2015 (12 Inch) have viewport size more than it's ratio, it is about 111% of it's viewport ratio.

MacBook 2015 (12 Inch) supports scaled lower resolutions listed below:
- 1440 x 900
- 1280 x 800
- 1024 x 640

MacBook 2015 (12 Inch) supports full native resolution on the built-in display and up to 3840 x 2160 pixels at 30Hz on an external display.

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

CSS Media Queries

MacBook 2015 (12 Inch) Media Queries (In terms of Mobile only)

@media only screen and (min-width: 1280px) and (max-width: 767px) { /* Your Styles... */ }

MacBook 2015 (12 Inch) Min-Width Media Queries

@media only screen and (min-width: 1280px) { /* Your Styles... */ }

MacBook 2015 (12 Inch) Min-Height Media Queries

@media only screen and (min-height: 800px) { /* Your Styles... */ }

MacBook 2015 (12 Inch) Landscape Media Queries

@media only screen and (min-width: 800px) and (orientation: landscape) { /* Your Styles... */ }

MacBook 2015 (12 Inch) Portrait Media Queries

@media only screen and (min-width: 1280px) and (orientation: portrait) { /* Your Styles... */ }

MacBook 2015 (12 Inch) Device Width Media Queries

@media only screen and (min-device-width: 1280px) and (orientation: portrait) { /* Your Styles... */ }
@media only screen and (min-device-width: 800px) and (orientation: landscape) { /* Your Styles... */ }

MacBook 2015 (12 Inch) Retina Media Queries

@media
  only screen and (-webkit-min-device-pixel-ratio: 2.0),
  only screen and (   min--moz-device-pixel-ratio: 2.0),
  only screen and (     -o-min-device-pixel-ratio: 2.0/1),
  only screen and (        min-device-pixel-ratio: 2.0),
  only screen and (                min-resolution: 226dpi),
  only screen and (                min-resolution: 2.0dppx) { 
    /* 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

@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

@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 */
}
                                

MacBook 2015 (12 Inch) Specifications

• Launch Date Early 2015
• macOS Sierra
• Physical Screen Size 12 INCH
• Resolution 2304 x 1440 PX
• Viewport Size 1280 x 800 PX
• Pixel Density 226 PPI
• Device-Independent Pixels 113 PPI
• Pixel Ratio 2.0 xhdpi  (111%)
• Width 2304 PX
• Height 1440 PX
• Device Width 1280 PX
• Device Height 800 PX
• Dimensions 0.35 x 28.05 cm (0.14 x 11.04 in)
• Weight 0.92 kg - 2.03 Pounds