Do you need HDMI 2.1 for 4K 120Hz? Cable and bandwidth requirements
35.6 Gbps is squarely in HDMI 2.1's wheelhouse. Any certified Ultra High Speed HDMI cable (48G) drives this mode without DSC. That avoids DSC processing, but the practical latency difference is tiny compared with the display's scanout and response behavior.
4K 120 Hz with 10-bit 4:4:4 color HDR needs 35.6 Gbps, the benchmark mode HDMI 2.1 was designed to support without compression. It sits 16% below HDMI 2.1's effective 42.6 Gbps ceiling, giving just enough headroom for the variable-rate timing overhead modern GPUs use.
By TechCompare · Updated
Interface Bandwidth Analysis
See how much uncompressed and compressed bandwidth this resolution and refresh rate mode demands, compared to HDMI and DisplayPort connections.
DSC uses visually lossless 3-to-1 compression, shrinking the required bandwidth so it fits through older cables.
Other connections
Assumes display traffic only and four DisplayPort lanes for USB-C. USB4 and Thunderbolt figures are for one DisplayPort stream.
Calculator
Display Bandwidth Calculator
Required Bandwidth
Uncompressed
35.64 Gbps
With DSC (Display Stream Compression)
9.50 Gbps
Interface Compatibility
HDMI
DisplayPort
Other connections
Assumes one display with no USB or PCIe data sharing. USB-C uses all four DisplayPort lanes. USB4 and Thunderbolt use the DisplayPort profile listed. The 120 Gbps modes add bandwidth for multiple streams, while one DP 2.1 UHBR 20 stream stays at 77.37 Gbps. Compare checks each display separately.
USB-C
Thunderbolt
USB4
How this is calculated
This is the mode that made HDMI 2.1 matter. HDMI 2.0 tops out at 14.4 Gbps and can't reach it even with 10-bit 4:2:0 chroma. Dropping only to 8-bit 4:4:4 also remains above the limit, so an uncompressed 4K 120 Hz fallback needs both a lower bit depth and reduced chroma, such as 8-bit 4:2:0, or a lower refresh or resolution. HDMI 2.1 handles the full mode natively without Display Stream Compression.
Verdict
The 35.6 Gbps the mode needs sits 16% below HDMI 2.1's effective 42.6 Gbps ceiling, which is exactly the headroom the spec was designed around for variable-rate timing overhead and modern GPU metadata. HDMI 2.0's 14.4 Gbps can't carry 10-bit 4K 120 Hz even with 4:2:0 chroma. With CTA-861 timing, 8-bit 4:4:4 is still about 28.5 Gbps, while 8-bit 4:2:0 is about 14.3 Gbps, so preserving 4K 120 Hz requires reducing both color depth and chroma, or instead lowering refresh or resolution. The DSC-free HDMI 2.1 path avoids codec processing, but any latency difference is tiny compared with the display's scanout, response time, and input path.
More HDMI 2.1 scenarios
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Frequently asked questions
Does PS5 require HDMI 2.1 for 4K 120Hz?
Does HDMI 2.0 support 4K at 120Hz?
Does Xbox Series X output 4K 120 Hz over HDMI 2.1?
What happens if I use an HDMI 2.0 cable for 4K 120 Hz?
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