Hong Life CalculatorsUnderstanding the screen resolution chart — concept and principle
This chart lists the common display and video resolutions, from HD (720p) to 8K UHD, with their pixel dimensions, total pixel count and size compared with Full HD. Use it to compare monitors, TVs, laptops and video export settings, or to understand what labels such as QHD, 4K and DCI 4K actually mean.
How it is calculated
Total pixels = width × height. The comparison with Full HD is total pixels ÷ 2,073,600 (the pixel count of 1920 × 1080). For example, QHD 2560 × 1440 = 3,686,400 pixels, or 1.78 × FHD. A related figure you can work out yourself is pixel density: PPI = √(width² + height²) ÷ diagonal in inches.
The principle
A digital image is a grid of pixels, so its detail grows with both dimensions at once. Doubling the width and the height multiplies the pixel count by four, which is why 4K UHD (3840 × 2160) is exactly four times Full HD and 8K UHD (7680 × 4320) is sixteen times. The consumer formats HD, FHD, 4K UHD and 8K UHD share a 16:9 aspect ratio and come from television standards (ITU-R BT.709 for HD, ITU-R BT.2020 for UHD). Cinema "DCI 4K" is a different, slightly wider format of 4096 × 2160 used in digital cinema projection.
Worked example
Default input: 4K UHD.
- Pixel dimensions: 3840 × 2160.
- Total pixels: 3840 × 2160 = 8,294,400.
- Compared with FHD: 8,294,400 ÷ 2,073,600 = 4.
- Result: 4K UHD is 3840 × 2160, 8,294,400 pixels, 4× Full HD.
How to read the result
More pixels only look sharper if the screen is big enough or you sit close enough to see them. That is why density matters: a 27-inch 4K monitor has about 163 PPI, while a 27-inch FHD monitor has about 82 PPI, and a 65-inch 4K TV only about 68 PPI but is viewed from much further away. Higher resolution also needs more graphics power: a game at 4K must render four times as many pixels per frame as at FHD, and uncompressed 8-bit RGB 4K at 60 frames per second is about 12 Gbit/s of raw data.
Common mistakes
- Calling QHD (2560 × 1440) "2K". In cinema, 2K means 2048 × 1080; QHD is closer to 2.5K.
- Assuming 4K means 4,000 pixels high; the "4K" refers to roughly 4,000 pixels of width.
- Comparing resolution without considering screen size and viewing distance.
- Expecting a 4K screen to improve low-resolution video; upscaling cannot add real detail.
FAQ
Frequently asked questions
How many pixels is 4K?
4K UHD is 3840 × 2160 = 8,294,400 pixels, about 8.3 megapixels.
What is the difference between 4K UHD and DCI 4K?
UHD is 3840 × 2160 (16:9) for TVs and monitors; DCI 4K is 4096 × 2160 for digital cinema, about 6.7 % more pixels.
Is 1440p worth it over 1080p?
QHD has 1.78 times the pixels, which is clearly visible on 27-inch monitors; on small laptop screens the difference is smaller.
Sources: ITU-R Recommendation BT.709, Parameter values for the HDTV standards · ITU-R Recommendation BT.2020, Parameter values for ultra-high definition television systems · Digital Cinema Initiatives, Digital Cinema System Specification