Screen Resolution Explained — HD, 4K, Retina, and What It All Means

Screen resolution describes how many individual dots of light — called pixels — make up a display. A display with more pixels packs more detail into the same physical area, producing a sharper image. A display with fewer pixels looks slightly rougher at close range, especially when displaying text or fine details.

Resolution is expressed as width by height in pixels. A 1920 by 1080 display — written as 1920×1080 — has 1,920 pixels across and 1,080 pixels from top to bottom. The shorthand "1080p" refers to this resolution. A 3840 by 2160 display — called "4K" or "2160p" — has four times as many pixels as 1080p, arranged in the same way but much more densely.

Here is the progression most people will encounter, from lowest to highest: 720p (1280×720) is called HD and is rarely used in new devices today. It looks soft on screens larger than about 27 inches. 1080p (1920×1080) is called Full HD and remains perfectly sharp for most people on screens up to about 27 inches. 1440p (2560×1440) is called QHD or 2K and is noticeably sharper than 1080p on computer monitors and laptops. 2160p (3840×2160) is called 4K or Ultra HD and offers the highest sharpness widely available in consumer devices.

"Retina" is Apple's marketing term for any display that is dense enough that individual pixels are not distinguishable at a normal viewing distance. It is not a specific resolution — different Apple devices use different resolutions under the Retina label. What it means in practice is that text looks very sharp and smooth on those screens.

Whether you can actually see the difference between resolutions depends on two things: the screen size and how far away you sit from it. The closer you are and the larger the screen, the more visible the difference becomes. On a 13-inch laptop screen you use at arm's length, 1080p and 1440p look very similar. On a 55-inch TV you watch from 10 feet away, 1080p and 4K are harder to distinguish than you might expect.