How fast can you copy 1 TB over Thunderbolt 4? Peak link rate

How this is calculated

In practice, Thunderbolt 4 is rarely the bottleneck. Modern NVMe-based Thunderbolt 4 enclosures often sustain about 2.5-2.8 GB/s writes, so 1 TB takes closer to 6-7 minutes in real use. That practical result is lower than the 40 Gbps peak-link calculation because the drive, PCIe tunnel, and protocol overhead become the limit. USB4 comes in 20 Gbps and 40 Gbps variants, so a USB4 enclosure needs a comparable PCIe storage path to match this estimate. Thunderbolt 5 raises the symmetric link to 80 Gbps and can provide more storage headroom.

Verdict

Thunderbolt 4's 40 Gbps figure is the peak aggregate link rate used by this calculator. Dividing a 1 TB file by that rate gives roughly 3 minutes 20 seconds before protocol and storage overhead. In practice sustained throughput on a fast external NVMe SSD often lands around 2.5-2.8 GB/s after DisplayPort tunneling, the 32 Gbps PCIe tunneling requirement (PCIe 3.0 x4 class), and protocol overhead take their cut, so the same 1 TB lands closer to 6-7 minutes on a real-world run. High-end video edit workflows and overnight SSD backups are exactly the transfer pattern where that time is routine rather than a weekend task, while USB 3.0's 35-60 minute per-terabyte math makes the same backup a chore.