4K HDMI Cable High Speed: Matching Class to Refresh Rate
Almost every cheap cable claims 4K. The variable that matters is refresh rate and colour depth, because those decide how much bandwidth the signal needs.
Quick Answer
| Signal | Bandwidth needed | Cable class |
|---|---|---|
| 4K at 30 Hz | Up to about 10.2 Gbps | High Speed is usually adequate |
| 4K at 60 Hz, 8 bit colour | About 12.5 Gbps | Premium High Speed |
| 4K at 60 Hz, 10 bit HDR | Up to 18 Gbps | Premium High Speed |
| 4K at 120 Hz | Beyond 18 Gbps | Ultra High Speed |
| 4K at 120 Hz with 10 bit HDR and full colour | Approaching 48 Gbps | Ultra High Speed |
If the signal exceeds the cable, the result is usually a drop to a lower refresh rate, loss of HDR, or intermittent blanking rather than a complete failure.
What Usually Goes Wrong
Colour compression
When bandwidth runs short, the source may reduce colour information. The image looks softer in fine detail and gradients band.
HDR switching off
A frequent symptom of an under capable cable or a long run beyond its limit.
Blanking at high refresh
The link renegotiates, causing a brief black screen when a game switches modes.
Sound dropouts
Audio and video share the link, so a marginal cable can affect both.
Choosing Correctly
- Note the resolution and refresh rate your display supports.
- Note whether HDR is in use and at what colour depth.
- Match the cable class to the requirement rather than to the version number.
- Measure the run and go active or optical if it is long.
- Test after installation by checking the reported resolution, refresh and HDR state.
Real-World Applications
- 4K televisions at 60 Hz with HDR.
- Monitors at 144 Hz for desktop work.
- Consoles outputting 4K at 120 Hz.
- Media players feeding a projector.
Related Guides
For the 48 Gbps class, read Ultra High Speed HDMI 2.1 cable. For long runs, see 50 foot HDMI cable. For set top boxes, start with HDMI cord for cable box.
FAQ
Do all 4K cables support HDR?
No. HDR at 60 Hz with 10 bit colour needs the Premium High Speed class or better.
Why did HDR turn off by itself?
Usually insufficient bandwidth. The source reduces the signal to fit the link.
Is a more expensive cable better for 4K?
Not beyond the class required. Certification matters more than price.
What length is safe for 4K at 60 Hz?
About five metres on passive copper, less for higher refresh rates.