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Transferring 1 TB over Thunderbolt 4 takes 3m 20s

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 8× 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)

Calculator

Data Transfer Calculator

Configuration

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.

Frequently asked questions

How long does it take to transfer 1 TB over Gigabit Ethernet?
At a theoretical 1000 Mbps (125 MB/s), 1 TB takes about 2 hours and 13 minutes in ideal conditions. Real-world speeds over Gigabit Ethernet typically top out around 110-115 MB/s due to TCP overhead, so budget closer to 2.5 hours for a full 1 TB copy.
Why is my real transfer speed slower than the cable's rated speed?
Rated speeds are raw signalling rates in bits per second. Protocol overhead (TCP/IP, USB framing, filesystem operations), encryption, small-file latency, and the slowest device in the chain (often the disk, not the cable) all reduce usable throughput. A USB 3.0 port rated 5 Gbps usually delivers around 400 MB/s in practice, not the theoretical 625 MB/s.
What's the difference between megabits (Mbps) and megabytes (MB/s)?
There are 8 bits in a byte, so 1000 Mbps equals 125 MB/s. Network speeds and ISP plans are advertised in megabits per second, while file sizes and storage speeds are measured in megabytes per second. Dividing Mbps by 8 gives you the MB/s figure you actually see when copying files.
How fast is WiFi 6 compared to Gigabit Ethernet for file transfers?
WiFi 6 can exceed Gigabit Ethernet on paper (up to ~9.6 Gbps theoretical) but real-world throughput usually lands between 500 Mbps and 1.5 Gbps depending on distance, interference, and client hardware. For a single large file transfer, wired Gigabit is still more consistent; WiFi 6E or WiFi 7 can edge ahead in ideal conditions.
Is USB 4 or Thunderbolt 4 faster for copying files?
Both use the same 40 Gbps underlying spec and deliver comparable real-world speeds of around 2800-3200 MB/s for sustained transfers. Thunderbolt 4 guarantees the full 40 Gbps and PCIe 32 Gbps tunnel; USB 4 allows 20 Gbps implementations, so check the port's actual spec rather than assuming parity.
Does file size affect transfer speed?
Yes — significantly. Transferring one 50 GB file hits near-maximum throughput, but copying 50 GB of small files (thousands of photos, say) can be 5-10x slower because every file has filesystem and metadata overhead. For large migrations, compressing into an archive first is often faster end to end.

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