This might be a completely stupid question because it is conceivably highly dependent on the respective disk speeds. But I am thinking that there is a speed cap that is specific to USB 2.0 that would by itself define a lower limit.

How long would it take to transfer 1TB of data from an external drive to an internal drive over USB 2.0?


13 Answers 13


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.

  • 8
    www39.wolframalpha.com/input/?i=1TiB+divided+by+53.248+MiB%2Fs about 5 hours 30 minutes
    – dbr
    Jul 20, 2009 at 13:44
  • 11
    You have to use 53.248 (theoretical maximum) × 0.6666666… (real-world limit) = 35.565333… MB/s. That's about 8 hours, 11 minutes and change.
    – phenry
    Jul 20, 2009 at 13:50
  • 5
    @theycallmemorty: 1 terabyte is (technically) 1,000,000,000,000 bits; 1 tebibyte = 1,099,511,627,776 bits. 1 short terabyte ÷ 35.5653 MiB/s = about 7 hours 27 minutes. Still quite a while.
    – phenry
    Jul 20, 2009 at 14:03
  • 2
    The difference between a TB and a TiB is 7%.
    – Guffa
    Jul 20, 2009 at 14:15
  • 3
    Real-world copy speed of USB2.0 is around ~15MB/s on windows. I've never seen 20MB/s and above.
    – Ergec
    May 28, 2013 at 6:28

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.

  • 1
    I've had the same experience across three machines and four USB HDDs. My best was 28MB/s (9-10 hours per TB). Mar 5, 2015 at 19:13
  • 1
    I run badblocks on a 1TB (i.e. 931 GiB) disk over USB2 and took very close to 10 hours which is 26,5 MiB/s or 27,8 MB/s (if I'm not mistaken with the MB, MiB and all that)
    – golimar
    Feb 4, 2016 at 21:29

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).

  • which system was that?
    – scjorge
    Jul 23, 2019 at 21:06
  • +1 for the TeraCopy link. Dec 16, 2020 at 19:30

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

  • 1TB @ 15 Mbit/s = 148 hours... wolframalpha.com/input/?i=1TB+at+15Mb/s
    – Feckmore
    Jul 20, 2009 at 14:32
  • 2
    @Traples Very correct. seems i made a typo. Should naturaly be 15 MB/s and not Mbit/s. updating answer. www08.wolframalpha.com/input/?i=1+TB+at+15+MB/s
    – pavsaund
    Jul 20, 2009 at 18:31
  • @pavsaund must've forgotten to update his answer, so I just edited it to be accurate and much clearer. Notice in Feckmore's Wolframalpha answer he mistakenly uses 15 Mbits/s, forgetting there are 8 bits in a Byte, so the answer in Megabytes (MB) is 148/8 = 18.5. (Interesting tidbit: his Wolframalpha link has a warning atop the answer saying "Assuming megabits per second for "Mb/s" | Use megabytes per second or mebibits per second instead Assuming terabytes (base 10) for "TB" | Use tebibytes (base 2) or more instead", which probably explains the difference between my 19.5 hr answer vs his 18.5h Dec 2, 2015 at 20:31

I have seen about 4-5x faster performance with ESata vs. USB2.0 using the same external hard drive. I have a WD 1.5TB Essentials Drive, which I would back up using USB, but it was painful, taking about 4-5hrs per 100G, and running about 8MB/sec avg. I pulled the HD out of the plastic case, removed the USB to SATA board, and plugged the same HD into the SATA port from the mother board via an ESATA cable, and I can now backup 100G in less than an hour, and 250G in about 2.5hr using NovaBackup S/W. All I can say is that 2-3hrs is not that bad for a lot of data (running about 28-32MB/sec w/ESATA). Both are well/far below theoretical, but the comparison between the two is what counts.


It's not just dependent on Disk speeds, but also the speed of the IDE/Sata controller on the external drive / USB key. I've found that many cheaper external drives are slower, they are still USB2 but have cheaper and slower IDE/Sata controllers.

Of course USB 2 has a theoretical max throughput of 480 Mbit /s [Clarified to stop uninformed comments], so you could work out pretty easily the absolutte fastest time (but this time would never happen in real life of course).

  • 2
    The max is 480 Mbps - megabits per second, not megabytes. There are 8 megabits in a megabyte. Jul 20, 2009 at 13:42
  • @Jared, Thanks for the condascending comment but since when does b stand for Byte? From Wikipedia "IEEE 1541 specifies "b" as the symbol for bit".
    – Ash
    Jul 20, 2009 at 13:48
  • As your comment was voted up obviously there are others slightly confused. It's simple: M = Mega B = Byte b = bit
    – Ash
    Jul 20, 2009 at 13:56

I just completed 2 of these transfers and I'm surprised at the slow USB 2.0 speed I'm getting. I copied 1 TB (terabyte) of video files and it took about 16 hours. Avg speed was in the 30's. The 2nd about a week later to a different external HD was 18 hours. And I was annoyed at the 1st transfer :)

time for esata external storage box with 4 or 5 bays!!!!


Depending on the file transferring rate, you can easily benchmark this copying a file of 100 Mb and try to extrapolate that to 1 Tb

With USB sticks I get about 4 Mb/s with large files from my MyBook I get 25 Mb/s

  • Point of reference 100MB * 10485 ~= 1Terrabyte. So however long that 100 MB takes, multiple by 10,485. Dec 4, 2010 at 22:11

Well, based on my rough calculations, somewhere around 7 hours and 15 minutes!

USB 2.0 has a raw data rate of 480Mbps, but the fastest typical usage usually tops out around 40 MB/s. Given that a terabyte has 1,048,576 megabytes, you just do the math.

If you could achieve the theoretical 60 MB/s transfer, you could do it in slightly over 4 hours and 45 minutes.


too many factors here. the write transfer rate to the disk will change depending on how much space you have used, I assume that RAID 0 is in play here and that you would be writing to a 1.5 TB drive considering that a 1 TB drive will not have 1 TB of free space available. Nevermind the same constraints for the source drives read transfer rate.

I reakon that ashh's answer would be correct if the drives' read and write constraints were not an issue {edit: and USB was running at max - not likely}.

but it would more likely slow down as the drive got fuller - taking about 30 - 45 mins longer. {edit: more real: 5-6 hrs longer}


As a real-world example, I just transferred 1.774TB worth of mixed files reading from USB2.0 and writing to USB3.0 on an old laptop with a 2nd generation i7, finishing in about 22 hours at a speed of about 22.6MB/s (which means about 12 hours for 1TB).


5400rpm Maxtor Green harddrive, or X25-E ultra high performance Intel solid state disk?

1TB worth of 1KB text files, or a 1TB video file?

For average transfers (mixed file size), on average harddrives (7200rpm consumer models), USB2 is not significantly slower then IDE or SATA - the speed difference you will encounter will be based almost entirely on overhead - more small files will result in slower transfer speeds. To get a speed measurement you will need to test using a real sample of the data you will be moving.


In both directions transfer is 480Mb/s. In one direction is 240Mb/s. Divide it by 8 to get bytes. So it is 30MB/s in one direction.

1TB = 1099511627776 bytes

1TB / 30MB = 34952,5(3) seconds

34952,5(3) / 60 seconds per minute = 582,54 minutes

582,54 minutes / 60 minutes per hour = 9.70 hour which gives 9 hours and 43 minutes to copy 1TB on USB 2.0 in one direction.

Not the answer you're looking for? Browse other questions tagged or ask your own question.