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HDMI 2.1 bandwidth for 4K at 120 Hz HDR is 33.4 Gbps

4K 120 Hz with 10-bit 4:4:4 HDR colour needs 33.4 Gbps — the benchmark mode HDMI 2.1 was designed to support without compression. It sits 22% below HDMI 2.1's effective 42.6 Gbps ceiling, giving just enough headroom for the variable-rate timing overhead modern GPUs use.

Required bandwidth
33.4 Gbps
Uncompressed
With DSC
8.9 Gbps
Visually lossless 3:1
Mode
3840×2160 @ 120 Hz
10-bit 4:4:4

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Required Bandwidth

Uncompressed

33.44 Gbps

With DSC (Display Stream Compression)

8.92 Gbps

Interface Compatibility

HDMI 1.4
✗ Incompatible
HDMI 2.0
DSC Required
HDMI 2.1 (48G)
✓ Native
HDMI 2.2 (96G)
✓ Native
DisplayPort 1.2
DSC Required
DisplayPort 1.4
DSC Required
DisplayPort 2.1 (UHBR 10)
✓ Native
DisplayPort 2.1 (UHBR 13.5)
✓ Native
DisplayPort 2.1 (UHBR 20)
✓ Native

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 4:2:0 chroma — you have to drop either refresh or bit depth. HDMI 2.1 handles it natively without Display Stream Compression, which is why PS5 and Xbox Series X require HDMI 2.1 cables for their 4K 120 Hz output modes.

Verdict

33.4 Gbps is squarely in HDMI 2.1's wheelhouse. Any certified Ultra High Speed HDMI cable (48G) drives this mode without DSC, keeping latency identical to a simpler 4K 60 signal.

More HDMI 2.1 scenarios

HDMI 2.1 — 4K 60 Hz
HDMI 2.1 (48G)
View details ➜
HDMI 2.1 — 4K 144 Hz HDR
HDMI 2.1 (48G)
View details ➜
HDMI 2.1 — 8K 60 Hz (4:2:0)
HDMI 2.1 (48G)
View details ➜

Frequently asked questions

Does HDMI 2.1 support 4K at 144Hz?
Yes. 4K at 144Hz with 10-bit HDR and 4:4:4 chroma needs roughly 40 Gbps of bandwidth, which fits within HDMI 2.1's 48 Gbps ceiling (42.6 Gbps effective data rate). You'll need a certified Ultra High Speed HDMI cable and a source and display that both advertise HDMI 2.1 FRL signalling.
Can DisplayPort 1.4 handle 4K at 240Hz?
Not uncompressed. 4K at 240Hz with 10-bit 4:4:4 requires about 65-70 Gbps — well over DisplayPort 1.4's 25.92 Gbps effective data rate. With Display Stream Compression (DSC), which is visually lossless, DisplayPort 1.4 can drive 4K at 240Hz comfortably. For uncompressed 4K 240Hz you need DisplayPort 2.1 UHBR 20.
What is Display Stream Compression (DSC) and is it lossy?
DSC is a visually lossless compression format standardised by VESA that cuts bandwidth roughly 3:1. In blind side-by-side testing the compression is indistinguishable from uncompressed output, so most modern high-refresh-rate monitors use it to reach 4K 240Hz or 8K 60Hz over existing cables. It does add a small amount of latency (microseconds) and can prevent some HDR metadata from passing through on older GPUs.
Why do I need more bandwidth for HDR and 10-bit colour?
Each pixel carries more data. 8-bit colour uses 24 bits per pixel (8 bits per channel × 3 channels) whereas 10-bit uses 30 bits per pixel — a 25% increase in required bandwidth. 12-bit adds another 20% on top of that. HDR content typically runs at 10-bit or 12-bit, which is why enabling HDR can push a connection over its limit.
What does 4:2:0 chroma subsampling do to bandwidth?
Chroma subsampling reduces colour resolution to save bandwidth. 4:4:4 carries full colour for every pixel; 4:2:2 halves horizontal colour resolution; 4:2:0 halves both horizontal and vertical colour resolution, cutting bandwidth by roughly 50% compared to 4:4:4. It's fine for video but makes coloured text on coloured backgrounds look fuzzy, so 4:4:4 is preferred for desktop use.
Is HDMI or DisplayPort better for a 4K 240Hz monitor?
Both can do it, but the route differs. HDMI 2.1 handles 4K 240Hz 10-bit natively if the display supports Frame Rate Control; DisplayPort 1.4 needs DSC, and DisplayPort 2.1 (UHBR 20) handles it fully uncompressed. For PCs, DisplayPort is typically the default; for consoles and TVs, HDMI 2.1 is the standard.

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