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Does HDMI 2.1 support 4K 240Hz? DSC, cable and bandwidth explained

By TechCompare · Updated · How we check

Yes, with DSC. Uncompressed 10-bit 4:4:4 needs 68.6 Gbps, more than HDMI 2.1's 42.6 Gbps effective rate, but with DSC the mode needs about 18.3 Gbps and fits.

Interface Bandwidth Analysis

See how much uncompressed and compressed bandwidth this resolution and refresh rate mode demands, compared to HDMI and DisplayPort connections.

Uncompressed Signal68.6 Gbps
With Display Stream Compression (DSC)18.3 Gbps

DSC uses visually lossless 3-to-1 compression, shrinking the required bandwidth so it fits through older cables.

Display Connection Reference
HDMI 2.0
14.4 Gbps
Not supported
HDMI 2.1 48G
42.6 Gbps
DSC required
HDMI 2.2 96G
85.3 Gbps
Native support
DP 1.4
25.9 Gbps
DSC required
DP 2.1b UHBR 20
77.4 Gbps
Native support
Other connections

Assumes display traffic only and four DisplayPort lanes for USB-C. USB4 and Thunderbolt figures are for one DisplayPort stream.

USB-C DP 1.4
25.9 Gbps
DSC required
Thunderbolt 5
77.4 Gbps
Native support
USB4 v2 80G / 120G
77.4 Gbps
Native support
Display Mode: 3840 × 2160 @ 240 Hz
Color depth: 10-bit 4:4:4
This exact 3840×2160 @ 240 Hz signal, pre-loaded. Swap the resolution, refresh, or chroma, or compare two modes.
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4K at 240 Hz with 10-bit 4:4:4 HDR needs 68.6 Gbps uncompressed. HDMI 2.1's effective rate is 42.6 Gbps, so the uncompressed mode is 61% more than the link can carry. DSC cuts it to about 18.3 Gbps, which is what makes this mode work on HDMI 2.1 at full color.

Cables for your display settings

HDMI and DisplayPort cable options for these settings. Choose the connectors your devices support.

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Both device ports must support the required display mode. A cable won't upgrade a port. Options marked DSC require compression support on both devices.

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How this is calculated

DSC is the only way to get full 10-bit 4:4:4 at 240 Hz on HDMI 2.1. It has to work at both ends, on the GPU and on the display. VESA describes DSC as visually lossless and low latency. The calculator's DSC figure of 18.3 Gbps assumes 8 bits per pixel after compression. Without DSC, 10-bit 4:2:0 (34.3 Gbps) fits natively, but it halves the color resolution across and down, so colored edges and small colored text soften. 8-bit 4:2:2 (36.6 Gbps) also fits, and it keeps full vertical color resolution.

Verdict

Use DSC for 4K 240 Hz on HDMI 2.1 when full color matters, and confirm that the GPU and the display both support it before you buy. If you can accept less color, 10-bit 4:2:0 or 8-bit 4:2:2 runs without DSC, though you give up some color detail. For uncompressed full color at this refresh rate, look at a DisplayPort 2.1 UHBR 20 link or an HDMI 2.2 port rated 96 Gbps.

More HDMI 2.1 scenarios

HDMI 2.1: 4K 60 Hz
4K at 60 Hz with 8-bit 4:4:4 color needs 14.3 Gbps of uncompressed bandwidth.
View details
HDMI 2.1: 4K 120 Hz HDR
4K 120 Hz with 10-bit 4:4:4 color HDR needs 35.6 Gbps, a mode HDMI 2.1 can carry without compression.
View details
HDMI 2.1: 4K 144 Hz HDR
4K 144 Hz with 10-bit 4:4:4 HDR needs 39.2 Gbps, within 8% of the calculator's effective 42.6 Gbps HDMI 2.1 model.
View details

Related guides

DSC explained
What DSC does, how much it compresses and which modes need it.
View guide
HDMI 2.2: 4K 240 Hz HDR
The same mode on HDMI 2.2, where the top tier carries it uncompressed.
View guide
DP 2.1: 4K 240 Hz HDR
The same mode on DisplayPort 2.1 UHBR 20, which carries it uncompressed.
View guide

Frequently asked questions

Does HDMI 2.1 do 4K 240Hz?
Yes, with Display Stream Compression (DSC). Uncompressed 10-bit 4:4:4 needs 68.6 Gbps, more than HDMI 2.1's 42.6 Gbps effective rate. With DSC the mode needs about 18.3 Gbps and fits. DSC has to be supported by both the GPU and the display.
Can HDMI 2.1 do 4K 240Hz without DSC?
Only with less color. 10-bit 4:2:0 needs 34.3 Gbps and 8-bit 4:2:2 needs 36.6 Gbps, and both fit natively. Full 4:4:4 color at 8-bit needs 54.8 Gbps, which still needs DSC.
Do I need a special cable for 4K 240Hz on HDMI 2.1?
Use an Ultra High Speed HDMI Cable. The HDMI Forum says that cable is for setups up to 48 Gbps, which matches the tier this page models.
Is DSC bad for image quality?
VESA describes DSC as visually lossless and low latency. Compression is the trade here: the calculator's DSC figure for this mode is 18.3 Gbps, against 68.6 Gbps uncompressed. The real result depends on the GPU and the display both supporting DSC.

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