How fast can you copy 1 TB over Thunderbolt 4? Peak SSD speed limitations

A 1 TB transfer over Thunderbolt 4 works out to 3 minutes 20 seconds at the interface's 40 Gbps peak rate. That's about 8x faster than USB 3.0 for the same file, which is why Thunderbolt's pitch has always been "external storage that's as fast as internal".

Transfer time

3m 20s

At peak link speed

File size

1 TB

1000 GB

Link speed

40,000 Mbps

Thunderbolt 4 / USB 4 (40 Gbps)

Configuration

File Size

Connection Speed

Mbps

Estimated Transfer Time

3m 20s

Speed Comparison

USB 2.0

4h 37m 46s

480 Mbps

USB 4 / Thunderbolt 4

3m 20s

40 Gbps

Selected

Gigabit Ethernet

2h 13m 20s

1 Gbps

10 Gigabit Ethernet

13m 20s

10 Gbps

WiFi 5 (ac)

5h 33m 20s

400 Mbps

WiFi 7 (be)

26m 40s

5 Gbps

SATA SSD

30m 18s

4.4 Gbps

NVMe Gen4 SSD

2m 22s

56 Gbps

How this is calculated

In practice, Thunderbolt 4 is rarely the bottleneck. Modern NVMe-based Thunderbolt 4 enclosures sustain ~28 Gbps (3.5 GB/s) write speeds, so 1 TB takes closer to 5 minutes in real use. Hitting the full 3m 20s requires both a top-tier drive (Samsung 990 Pro class) and a system that can feed data that fast from the source. USB 4 (also 40 Gbps) performs identically for this transfer. Thunderbolt 5 bumps to 80 Gbps symmetric, cutting the theoretical time to 1m 40s.

Verdict

3m 20s for 1 TB is the high-end edit-workflow benchmark. If you're backing up a full SSD over lunch, Thunderbolt 4 is the interface that makes it routine rather than a weekend task.