Can Thunderbolt 4 run two 4K monitors?
AnswerYes
Yes, two 4K 60 Hz monitors is a Thunderbolt 4 requirement. Each needs 12.54 Gbps, 25.08 Gbps for both, inside a 40 Gbps link that still has room for USB data. Two 4K 120 Hz or 144 Hz screens is a different matter: that's beyond what Thunderbolt 4 guarantees, and only some setups manage it with DSC. Macs with base M1/M2/M3 chips support fewer external displays than the port allows.
Each 4K 60 Hz monitor
| Link | Needs | Has | Result |
|---|---|---|---|
| Thunderbolt 4 | 12.54 Gbps | 25.92 Gbps | Fits |
How the numbers are worked out
Reduced-blanking timing (VESA CVT-R2)
3840×2160 active → 3920 × 2222 total pixels per frame
3920 × 2222 × 60 Hz = 522.61 MHz pixel clock
522.61 MHz × 24.0 bits per pixel = 12.54 Gbps
8-bit colour, full RGB/4:4:4: 3 × 8 = 24.0 bits per pixel.
"Has" is the link's usable rate after line coding. DSC is modelled as up to 3:1 compression. Full method.
Each 4K 144 Hz monitor, 10-bit
| Link | Needs | Has | Result |
|---|---|---|---|
| Thunderbolt 4 | 39.19 Gbps13.06 with DSC | 25.92 Gbps | With DSC |
A Thunderbolt 4 dock with two video outputs, or two monitors daisy-chained through a Thunderbolt monitor, both work. Windows also supports DisplayPort MST hubs. macOS doesn't, so on a Mac use a Thunderbolt dock or two separate ports.
The standards involved
Thunderbolt 4
The same 40 Gbps as Thunderbolt 3, with the minimums raised so every port behaves the same.
- data: 40 Gbps (PCIe 32 Gbps)
- video: two 4K 60 Hz or one 8K
- power: up to 100 W (USB PD)
USB4 (20 and 40 Gbps)
Thunderbolt 3's protocol, opened up as a USB standard. Tunnels USB, DisplayPort and PCIe over one cable.
- data: 20 or 40 Gbps
- video: DisplayPort tunnelled
- power: USB PD required
Thunderbolt 5
80 Gbps both ways, 120 Gbps towards displays. Intel's certified USB4 Version 2.0.
- data: 80 Gbps (120 boost)
- video: multiple 4K 144 Hz / 8K
- power: up to 240 W