4K Isn't Just Marketing: Name Comes From 2005 Cinema Standard
4K isn't just marketing; Engadget says the name came from a 2005 cinema standard and equals four times 1080p.
The 4K used in consumer TVs and monitors is technically different: it is 3,840 by 2,160 pixels. As Engadget explains, that format is exactly four times the size of 1080p full HD, which is 1,920 by 1,080 pixels. Both horizontal and vertical counts are doubled, and the label has stuck because of that scaling, even though the DCI cinema version has a slightly wider frame.
Confusion often arises because multiple terms refer to similar resolutions. Ultra HD (UHD) is a general adjective used alongside 4K. The more technical name for consumer 4K is 2160p, which follows the older naming pattern of 480p, 720p and 1080p. The "p" stands for progressive, meaning the entire frame is drawn in one pass rather than alternating odd and even lines as in interlaced "i" standards. Between 1080p and 4K sits QHD, at 2,560 by 1,440 pixels, also called 1440p or 2K; it is four times the area of 720p rather than 1080p.
Having a 4K TV does not guarantee 4K content, the report notes. Most broadcast TV remains 720p or 1080i. Streaming services such as Netflix, HBO Max and Prime Video often reserve 4K for higher-priced plans. Game consoles like the PlayStation 5, Xbox Series X and Nintendo Switch 2 can output 4K, but performance modes may lower the resolution to favor frame rate. Watching 4K movies on disc requires a 4K Blu-ray player and 4K Blu-ray discs, plus an HDMI 2.0 cable at minimum for 4K output; HDMI 2.1 enables higher refresh rates. Some sources claim 4K but are actually upscaled, with the TV adding missing pixels to lower-resolution content.