Digital storage · interfaces
USB, SATA and Ethernet transfer time.
Enter a file or backup size to see the best-case copy time over each common interface, with the payload rate in MB/s.
Inputs
Best-case times
Enter the numbers above.
How long does a copy take over USB, SATA or Ethernet?
Each interface has a published line rate: USB 2.0 High Speed 480 Mbit/s, USB 3.2 Gen 1 5 Gbit/s, Gen 2 10 Gbit/s, Gen 2x2 20 Gbit/s, USB4 and Thunderbolt 3 and 4 40 Gbit/s, SATA III 6 Gbit/s, and Ethernet at 1, 2.5 and 10 Gbit/s. Where the encoding is documented, the tool removes it: 8b/10b (USB 3.2 Gen 1 and SATA III) carries 80 percent of the line rate as data, and 128b/132b (USB 3.2 Gen 2 and 2x2) about 97 percent. That gives 500 MB/s for USB 3.2 Gen 1, 600 MB/s for SATA III and 2,424 MB/s for Gen 2x2, matching the cited figures. Time is size divided by that payload rate.
Worked example. Copying 100 GB over Gigabit Ethernet at 125 MB/s takes 800 seconds (13 minutes 20 seconds). Over USB 3.2 Gen 1 at 500 MB/s it takes 200 seconds (3 minutes 20 seconds); over USB 2.0 at 480 Mbit/s it takes 1,667 seconds (27 minutes 47 seconds). These are ceilings: the drive, cable, controller and file sizes usually limit real copies well below them, which is what the percentage box is for.
Frequently asked questions
How long does it take to copy 100 GB over USB 3?
Over USB 3.2 Gen 1 the best case is about 200 seconds (500 MB/s); the real time depends mostly on the drive.
Is the interface or the drive the bottleneck?
Often the drive. A hard disk is much slower than a USB 3 or SATA III link, so the interface limit is rarely reached with spinning disks.
Why is Gigabit Ethernet about 125 MB/s?
1,000 megabits per second divided by 8 bits per byte is 125 megabytes per second, before protocol overhead.
Are USB4 and Thunderbolt the same speed?
Both are listed at 40 Gbit/s in the cited sources; real throughput depends on the devices and tunnelled protocols.
Sources
Checked
- Wikipedia, "USB", opened 15 October 2026. USB 2.0 High Speed 480 Mbit/s; USB 3.2 Gen 1 5 Gbit/s (8b/10b, 500 MB/s); Gen 2 10 Gbit/s and Gen 2x2 20 Gbit/s (128b/132b, 2424 MB/s for Gen 2x2); USB4 40 Gbit/s
- Wikipedia, "Thunderbolt (interface)", opened 15 October 2026. Thunderbolt 3 and 4 run at 40 Gbit/s
- Wikipedia, "Serial ATA", opened 15 October 2026. revision 3.0: 6 Gbit/s, 600 MB/s
- Wikipedia, "2.5GBASE-T and 5GBASE-T", opened 15 October 2026. 1000BASE-T 1 Gbit/s, 2.5GBASE-T 2.5 Gbit/s, 10GBASE-T 10 Gbit/s
- NIST, "Prefixes for binary multiples", opened 15 October 2026. kibi, mebi, gibi, tebi are 2^10, 2^20, 2^30, 2^40; under SI mega means 1,000,000, so 1 MB = 10^6 bytes and 1 GB = 10^9 bytes
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Scope
Best-case ceilings from published line rates. Drives, cables, controllers, protocol overhead and file patterns lower real transfer speeds.