What is 4K TV and Ultra HD? All you need to know about 4K

The world of TVs has moved on a lot in the past few years. There are new technologies and certifications, all aimed at making the next leap forward, none more so than 4K TV.

They all carry snappy acronyms such as HDR10+, Dolby Vision HDR and 8K. For now, the main one you need to know is 4K.

4K is no longer something for early adopters, but is now coming into its own as studios, broadcasters and streaming services support it.

Netflix and Amazon have pushed 4K greatly on their streaming platforms in the past few years, with the latter also offering several 4K compatible devices. There’s also Sky Q, which brings 4K to a whole new segment of mainstream TV viewers in the UK. On the gaming side, there’s 4K love from the Xbox One X and PS4 Pro. There’s also Apple’s attempt to storm the 4K castle with its Apple TV 4K.

With all that in mind, here’s everything you need to know about 4K, to save you a load of time and effort when buying a new 4K TV.

What is 4K?

4K, also known as Ultra HD, refers to a TV resolution of 3,840 x 2,160 pixels. That’s four times as many pixels than in a full HD TV, a total of about 8.3 million pixels. Having so many pixels means a higher pixel density, and you should have a clearer, better defined picture. It’s not necessarily about sharpness, but about letting more detail and texture through.

Related: Best 4K TV

We continually check thousands of prices to show you the best deals. If you buy a product through our site we will earn a small commission from the retailer – a sort of automated referral fee – but our reviewers are always kept separate from this process. You can read more about how we make money in our Ethics Policy.

Google Chromecast Audio Deal

Google Chromecast Audio

Pick up a Google Chromecast Audio (or two, or three...) for a discounted price before they're gone forever.

What is the difference between 4K and Ultra HD?

4K is more commonly used, but you’ll also find people calling it Ultra HD, or UHD. For the average consumer buying a TV, these are one and the same. But there is a small difference.

In its correct usage, true 4K refers to a resolution of 4096 x 2160, which was first introduced in digital cinemas. UHD refers to a resolution of 3840 x 2160, which is the resolution you actually get on the TVs you take home.

So technically, 4K is the wrong term for 3840 x 2160 displays and content, but it’s said so often that two terms are interchangeable.

Related: Netflix vs Amazon Video

Sony A1E AE1 4K OLED TV

What does 4K offer?

Simply, the extra resolution of 4K adds better definition and clarity. The result is images that look life-like, closer to looking through a window rather than watching TV.

4K TV is especially effective on very large screens – so ideally you’d settle for a 55-inch set or go even bigger. The effect is more noticeable if you’re moving to 4K from a TV of the same size.

Let’s say you have a 50-in HD TV and you upgrade to 4K: you are cramming four times the number of pixels into the same amount of space and that makes for a noticeably denser picture with finer detail.

8K has hit the market, although it’s still in its infancy there are 8K screens available to buy. They are, expensive, however, and will need a screen of at least 65in to get the best out of them. There’s also no native 8K content to watch at the moment.

8K won’t achieve mainstream acceptance (or affordability) for a while yet, so you’re safe to buy your 4K TV unless you’re desperate for the features that 8K brings with it.

Related: What is 8K?

How close do I need to sit to the TV?

To get the best out of 4K, it is recommended that you sit closer to your screen than you would do with HD. The extra resolution and increased pixel density means you can sit further forward to get the most from your TV. And filling up more of your field of view makes for a more immersive experience.

While sitting close gives you the most impact, we reject the notion that there’s no benefit from distant viewing positions. Lines are still cleanly drawn, you still perceive more depth, colours still look more subtly and smoothly rendered, and objects within the picture still look solid and three-dimensional.

Related: Best TV Deals

4K packs in four times the number of pixels as Full HD / 1080p.

What else do I need to start watching 4K TV?

While your 4K TV will upscale HD and standard definition pictures to 4K, you’ll still need a native 4K source if you want to take advantage of your TV.

Examples include 4K streaming services like Netflix and Amazon, several 4K streaming sticks, Apple TV 4K, as well as Ultra HD Blu-ray players.

Related: 4K Ultra HD Blu-ray

Where can I watch 4K content?

There are several ways to catch 4K content. If you’ve sworn off physical and are ensconced in streaming services, your main options are Netflix and Amazon Video. The former has an ever-expanding library of TV series and films to stream in 4K for £9.99/month.

In terms of TV, you’ve got the likes of Unbreakable Kimmy Schmidt, Maniac and Narcos. Netflix’s original films  offer a few notable efforts including Apostle, Okja and Mute. There are also films from other studios to watch on the service, as well as comedy specials and documentaries.

Amazon Prime Video offers 4K content as part of its video streaming service, including original Amazon series such as Mozart in the Jungle, Homecoming, and All or Nothing: Manchester City.

BT has also has a 4K TV channel in BT Sport Ultra HD. It shows Premier League, FA Cup and Champions League football along with Aviva Premiership rugby. You’ll need one of BT’s Ultra-HD boxes to take advantage of the service.

Then there’s the Sky Q service, where you can watch the broadcaster’s sizeable catalogue of films and TV shows in 4K, with most Premier League football games broadcast in 4K too.

Related: Sky Q review

Panasonic EZ952 / EZ950 17

Do all 4K TVs support 4K streaming?

These days, yes. The first 4K TVs that came out in 2013 couldn’t handle Netflix 4K streams. Netflix adopted the HEVC video format and none of the TVs could decode it. These days, you’ll struggle to find a 4K TV that cannot stream and does not have access to 4K streaming services.

What internet speed do you need to stream 4K TV?

Netflix and Amazon require speeds of at least 15Mbps to stream 4K content. Speeds need to remain consistently at or above that figure; as soon as you drop – let’s say due to high contention rates at peak usage times – the picture will slip back into HD. And don’t worry if you start off with a blurry image: it’s common for streaming services to start a programme at low resolution and then bump it up to HD and UHD after the initial buffer.

To try and cover itself for this eventuality, Netflix actually says on its website that you need 25Mbps minimum. But we’ve confirmed with Netflix that a consistent 15Mbps is enough. It’s worth bearing in mind that this means you need 15 to 25Mbps of spare bandwidth, so if someone else is using your Wi-Fi, you’ll need to have that amount of bandwidth free after you account for the other person’s usage.

Compression techniques improve all the time, so it’s possible you may in the future need slightly lower broadband speed to experience 4K on Netflix or other rival 4K streaming platforms. But bear in mind that high levels of compression can negatively affect picture quality, so if you’re serious about 4K a fast broadband connection is a must.

What is UHD Blu-ray?

We’ve got a detailed breakdown of UHD Blu-ray, for a full rundown of the new format. In short, Ultra HD Blu-ray discs have a much larger capacity than standard Blu-ray discs, and can carry the information needed to store 4K video without the compression of streaming sites. Basically, it’s the best form of 4K you can watch at home.

There are plenty of UHD Blu-ray players out now, including the Panasonic DP-UB9000 and Sony UBP-X700. Microsoft provides an affordable alternative in the Xbox One S, which plays 4K Blu-rays alongside games.

What connections do I need to watch 4K?

We’d love to say ‘an HDMI socket’ and leave it at that, but unfortunately it’s not that simple.

The issue here is that not all HDMI sockets are equal. There have been multiple versions/standards of HDMI since the digital connection first appeared, with the latest v2.0 HDMI specification being defined specifically with 4K feeds in mind.

The most significant advantage of HDMI 2.0 is that they support increased data bandwidth, and so enable playback of 4K feeds with full (so-called 4:4:4) colour sampling at frame rates of up to 60fps. The previous HDMI 1.4 supports 4K feeds up to 30fps.

Most of the major 4K TV brands now carry HDMI 2.0 in their current TVs – LG, Sony, Panasonic and Samsung are all onboard with it now, as is Philips.

Related: What is HDR TV?

Can I make my own 4K content?

You can. There are domestic cameras capable of producing startlingly good 4K quality without costing the earth. Two of the best examples are the £1,500 Sony FDR-AX700 camcorder and the (body only) Sony A6400 camera.

Many modern smartphones are also capable of capturing 4K video, including Apple’s iPhone 8 and iPhone X. Of course, 4K recording has long been supported at the top end of the Android market, and 4K video capture is present on current flagships such as the Samsung Galaxy S10+, HTC U12+, and the LG G6.

Unlike other sites, we thoroughly review everything we recommend, using industry standard tests to evaluate products. We’ll always tell you what we find. We may get a commission if you buy via our price links. Tell us what you think – email the Editor