How long would it take to transfer 1TB over USB 2.0?

USB 2.0 has a signaling rate of 480 Mbit/s. The same article says that typical real-world throughput is "about two thirds of the maximum theoretical bulk data transfer rate of 53.248 MB/s." If my math is correct, and it probably isn't, that suggests that the best time you could hope to achieve is about 8.2 hours for 1 TB, assuming that the USB connection is the biggest bottleneck.

There is a lot of false information in these answers about "theoretical" performance from people who have evidently never benchmarked USB2 HD transfer rates.

I have benchmarked many different USB2 transfers between 2.5" laptop HDs both PATA and SATA, 3.5" HDs both PATA and SATA, and USB Flash drives...

...and I have NEVER seen transfer rates exceed 35 MB/sec! In fact, any properly configured modern drive will transfer at 20-30 MB/sec, it's very rare to see the 30 MB/sec rate be surpassed. (I'm referring SPECIFICALLY to HDs transferring over USB2 here, to be clear.)

Ignore this talk about theoretical transfer rates and "60 MB/sec", etc. Although I give credit to the guys who correctly converted bits into bytes and calculated a 35 MB/sec maximum, which falls in line with my REAL WORLD PERFORMANCE EXPERIENCE.

From experience, I know USB 2.0 copies about 10Mb/sec on average (on my system).

So that would be
1TB == 1048576 Mb
1048576 / 10 ==> +/- 104857 secs
104857 / 60 ==> +/- 1747 mins
1747 / 60 ==> +/- 29 hours

So a full day and 5 hours.

Note that I use teracopy as the default copy handler of my windows (otherwise I never get the 10Mb/sec average over usb).

Given the variations of I/O handling by the operating system and the natural delay of starting and stopping copying (many vs few files) you are realisticly looking at approx 15 Mbit/s (from my experienve)

Theoretical values: 1 TB @ 480 MBit/s = approx 4.6 hrs

Realistic values: 1 TB @ 15 MBit/s = approx 148 hrs