What is 4K resolution?
4K resolution is 3840 × 2160 pixels, known as 4K UHD (Ultra HD): 3,840 pixels across and 2,160 down. That is 8.3 megapixels in a 16:9 frame, exactly four times Full HD. Digital cinema uses a slightly wider frame, DCI 4K, at 4096 × 2160 pixels.
The name 4K is the rounded width of the picture, about 4,000 pixels. The two sizes come from two different standards:
- 4K UHD, 3840 × 2160: TVs and monitors. Recommendation ITU-R BT.2020 defines UHDTV in two sizes, 3840 × 2160 and 7680 × 4320, with square pixels and a 16:9 aspect ratio.
- DCI 4K, 4096 × 2160: digital cinema. The Digital Cinema Initiatives specification (DCSS 1.5.1) sets a 4096 × 2160 container for 4K distribution and 2048 × 1080 for 2K. That is 8.8 megapixels at about 1.9:1.
2160p is the same resolution named after its 2,160 lines of vertical resolution. YouTube Help lists it as “2160p (4K): 3840 × 2160”. The p stands for progressive scan, full frames without interlacing, and BT.2020 allows progressive only.
Read more:
4K vs 1080p, 1440p and 8K: resolution chart
4K UHD has exactly four times the pixels of Full HD: twice as many across and twice as many down (8,294,400 against 2,073,600).
| Name | Size (px) | MP | Where you see it |
|---|---|---|---|
| SD (576 lines) | 720 × 576 | 0.4 | SD TV (ITU-R BT.601), 4:3 picture |
| HD (720p) | 1280 × 720 | 0.9 | YouTube 720p |
| Full HD (1080p) | 1920 × 1080 | 2.1 | HDTV (ITU-R BT.709), YouTube 1080p |
| QHD, “2K” on YouTube (1440p) | 2560 × 1440 | 3.7 | QHD monitors, YouTube 1440p |
| 4K UHD (2160p) | 3840 × 2160 | 8.3 | 4K TVs and monitors, YouTube 2160p |
| DCI 4K | 4096 × 2160 | 8.8 | digital cinema |
| 5K | 5120 × 2880 | 14.7 | 5K monitors, e.g. Apple Studio Display |
| 8K UHD (4320p) | 7680 × 4320 | 33.2 | 8K TVs, YouTube 4320p |
“2K” means two different things: YouTube uses it for 2560 × 1440, while in cinema DCI 2K is 2048 × 1080, close to Full HD.
4K vs 1080p: can you see the difference?
It depends on screen size and viewing distance. Recommendation ITU-R BT.1845 assumes the eye resolves detail of one arc minute.
On that basis, 4K shows its full benefit at 1.6 picture heights or closer. From 3.2 picture heights away, the eye can no longer resolve even Full HD pixels, so the difference practically disappears.
- 55-inch TV (picture about 68 cm high): full 4K within about 1.1 m (3.6 ft), no difference from about 2.2 m (7.2 ft).
- 65-inch TV (about 81 cm): full 4K within about 1.3 m (4.3 ft), no difference from about 2.6 m (8.5 ft).
- 27-inch monitor (about 34 cm): full 4K within about 54 cm (21 in), no difference from about 1.1 m (3.5 ft).
4K quality is more than resolution: more pixels do not mean better colour or contrast. Besides resolution, BT.2020 defines a wider colour gamut and 10 or 12 bits per component, while HDR is covered by a separate recommendation, ITU-R BT.2100. A 4K TV can have poor contrast and a Full HD screen good contrast.
4K in photography: is 8.3 MP a lot?
For a photo, 4K is a modest resolution. The Canon EOS R we used for the comparison below records 6720 × 4480 px, or 30 MP, about 3.6 times as many pixels as 4K.
Pixel count does not tell you whether a photo is sharp, though. Product photography with zoomable detail needs the most headroom, for example jewellery photos or macro.
The same detail in Full HD, 4K and native resolution
We took a packshot of an Urbannote candle (Towarzyski Wrocław, 190 g, a jar 7 cm across) and downscaled it with the Lanczos filter to Full HD, 4K and 4480 × 2520 px, the way an export from an editing app does. From each version we cut the same part of the label, about 1 × 1 cm, and enlarged it to one size.
The third version is the camera’s own resolution: the Canon EOS R records a square of up to 4480 × 4480 px, so no column is upscaled. We shot it with a 180 mm macro lens at f/18 so that the depth of field covers the whole label.
- Full HD: the crop is 96 × 96 px; enlarged, the letters have soft, stepped edges.
- 4K: 192 × 192 px, the text is sharp and readable.
- Native resolution: 224 × 224 px, it looks almost like 4K because it has only 17% more pixels across.
4K print size: how big can you print?
Print size in inches is pixels divided by dpi. At 300 dpi a 3840 × 2160 file prints at 12.8 × 7.2 in (32.5 × 18.3 cm), because 3840 / 300 = 12.8. What dpi means and when it matters is explained in our glossary entry DPI and image resolution.
| File | MP | Full 4K UHD? | Print at 300 dpi |
|---|---|---|---|
| Full HD, 1920 × 1080 | 2.1 | no | 6.4 × 3.6 in (16.3 × 9.1 cm) |
| 4K UHD, 3840 × 2160 | 8.3 | yes | 12.8 × 7.2 in (32.5 × 18.3 cm) |
| shop square, 2000 × 2000 | 4.0 | no | 6.7 × 6.7 in (16.9 × 16.9 cm) |
| 24 MP camera, 6000 × 4000 | 24.0 | yes | 20 × 13.3 in (50.8 × 33.9 cm) |
| 6K square, 6000 × 6000 | 36.0 | yes | 20 × 20 in (50.8 × 50.8 cm) |
Is my photo 4K? Check it in your browser
The tool below reads your photo’s dimensions and shows the same as the table: megapixels, whether it is full 4K UHD (at least 3840 × 2160 px, landscape or portrait), whether it fits a 4K screen without upscaling and its print size at 300 dpi.
Choose a photo or type in its dimensions.
The photo stays on your device: the browser only reads its dimensions.
The tool needs JavaScript. Results for typical files are in the table above.
- Dimensions
- Megapixels
- On a 4K UHD screen (3840 × 2160)
- Print size at 300 dpi
In camera and smartphone specs, “4K” describes video recording. Photo resolution is listed separately, in megapixels: compare that number with the 8.3 MP in the table.
Headroom for cropping
At marszalstudio we retouch the full camera file and export smaller versions at the end.
Headroom matters most when you crop: from a 6720 px Canon EOS R file you can cut away half the width and still have 3360 px, more than a 2000 × 2000 shop square. The same cut leaves 960 px from a Full HD file.
Do product photos need to be 4K?
Usually not, because marketplaces scale photos down anyway. The Amazon product image guide (the same on amazon.com and amazon.co.uk) sets:
- a minimum of 500 px and a maximum of 10,000 px on the longest side;
- 1,000 px or more for zoom, which Amazon recommends for the best customer experience;
- no artificial enlarging of small images.
eBay (the same rules on ebay.com and ebay.co.uk) asks for at least 500 × 500 px, recommends about 1600 × 1600 and accepts files up to 12 MB. A 4K file is more than either platform needs.
Keep the full-resolution file for print and upload a smaller WebP or AVIF version to your own shop, because a large file slows the page down. Amazon recommends JPEG; eBay also accepts WebP and AVIF.
At marszalstudio a 2000 × 2000 px packshot file is included in the price. A larger size, 6K (6000 px) or a custom size from your brief, is an extra €3 net per photo (product photography pricing, how to order a shoot).
Pro tip: export shop, banner and print versions from the largest file you have, always downwards. Upscaling Full HD to 4K adds pixels but not detail, as the comparison above shows.
4K video
4K video on YouTube is 2160p. 4K recording is no longer limited to cinema cameras: action cameras and many smartphones offer it too.
How much space does 4K video take?
- A file for YouTube: the recommended bitrate is 35-45 Mbps at 24-30 frames per second (YouTube Help), or about 263-338 MB per minute (35 × 60 / 8 = 262.5 MB).
- Uncompressed: 3840 × 2160 pixels × 3 bytes (8 bits per colour) is 24.9 MB per frame, about 37 GB per minute at 25 frames per second.
An hour of uncompressed 4K video (8 bits per colour, 25 frames per second) takes about 2.2 TB
What you need to edit and watch 4K
Even compressed 4K footage is hundreds of megabytes per minute, so editing needs a fast drive and a powerful computer. To watch it you need three things:
- a 4K UHD screen (at least 3840 × 2160 under the CTA definition) with at least one HDMI input that supports HDCP 2.2, which CTA requires of a 4K UHD screen;
- content recorded or streamed in 4K;
- for YouTube, a browser or device that supports the VP9 codec.
What comes after 4K: 8K and HDR
The next step is 8K UHD: 7680 × 4320, four times the pixels of 4K and sixteen times Full HD. It is defined in the same BT.2020, and from 2020 models CTA awards an 8K Ultra HD logo to screens with at least 33 million pixels. According to BT.1845 you get the full 8K benefit at 0.8 picture heights or closer, about 65 cm (2.1 ft) from a 65-inch TV.
The other direction is HDR (ITU-R BT.2100): a wider range of brightness and colour instead of more pixels. High resolution also matters in virtual reality (VR) and augmented reality (AR) headsets, where the screen sits right in front of the eye.
4K resolution: frequently asked questions
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Is 3840x2160 4K?
Yes. 3840 × 2160 pixels is 4K UHD, the 4K used by TVs, monitors and YouTube: 8.3 megapixels in a 16:9 frame. Digital cinema uses the wider DCI 4K, 4096 × 2160 pixels.
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Is 4K the same as 2160p?
Yes. 2160p is the same 3840 × 2160 resolution named after its 2,160 lines, just as 1080p means Full HD. The p stands for progressive scan: full frames without interlacing.
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How many megapixels is 4K?
4K UHD has 8,294,400 pixels, about 8.3 megapixels, and DCI 4K has 8.8. That is less than most cameras record: a 24 MP photo has almost three times as many pixels.
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Which is better, 1440p (2K) or 4K?
4K has more pixels: 8.3 MP against 3.7 MP for 2560 × 1440, which YouTube calls 2K. In cinema 2K means 2048 × 1080. 4K pays off on large screens viewed up close.
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Is 4K better than 1080p?
4K has four times the pixels, but the difference only shows up close. On a 65-inch TV the full benefit needs about 1.3 m (4.3 ft); beyond 2.6 m (8.5 ft) it disappears (ITU-R BT.1845).
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What do I need to watch 4K?
A 4K UHD screen (at least 3840 × 2160), 4K content and a source that can send it, for example over HDMI with HDCP 2.2. YouTube in 4K needs a browser or device with VP9.
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How much space does 1 minute of 4K video take?
It depends on compression. At YouTube’s recommended bitrate (35-45 Mbps at 24-30 fps) a minute takes about 263-338 MB. Uncompressed, a minute of 4K at 25 fps takes about 37 GB.
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Do product photos need to be 4K?
Usually not. Amazon enables zoom from 1,000 px on the longest side and eBay recommends about 1600 × 1600. At marszalstudio a 2000 × 2000 px file is included in the price.
Summary
- 4K resolution is 3840 × 2160 pixels (4K UHD): 8.3 MP in 16:9. Cinema uses DCI 4K, 4096 × 2160.
- 4K has four times the pixels of Full HD, but you only see the difference up close or on a large screen.
- In photography 4K is a modest 8.3 MP: enough for a screen and a 12.8 × 7.2 in print at 300 dpi.
- Online shops rarely need 4K: Amazon enables zoom from 1,000 px and eBay recommends about 1600 × 1600.
Need product photos sized for your shop and marketplaces? See our product photography prices, or learn how to remove a background from a photo yourself.
