4K, also called Ultra HD or UHD, refers to a resolution with roughly 4000 horizontal pixels. For consumer TVs, monitors and streaming, it normally means 3840 by 2160 pixels, which is exactly four times the pixels of 1080p (1920 by 1080).
Why it matters
More pixels give a sharper image, especially on large screens or at close viewing distances. The cost is that everything gets heavier: games need a stronger GPU to hold a good frame rate, video files and streams need more bandwidth, and cables and ports must support the needed data rate. Digital cinema 4K is slightly different at 4096 by 2160.
Example
Pixel counts:
- 1080p: 1920 x 1080 = 2,073,600 pixels
- 4K UHD: 3840 x 2160 = 8,294,400 pixels
A game that ran at 100 FPS in 1080p may run far slower at 4K, since the GPU must shade four times as many pixels per frame. Upscaling features can reduce that cost.
Common mistakes
- Buying a 4K display without checking that the HDMI or DisplayPort cable and port support 4K at 60 Hz.
- Expecting a visible gain on a small screen at long distance.
- Assuming 4K streaming is guaranteed; it also depends on the plan, device and connection.
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