Clear all

USB 3.0 Transfer Speeds  


Topic starter

I have a late 2013 13" MacBook Pro.  According to System Information, the USB ports are USB 3.0.  I just picked up a SanDisk Ultra Fit USB 3.1 Flash Drive, 256 GB, to move my Pictures folder to, off my SSD (These are not in the Photos app).

The Copy window says I'm moving 175.16 GB, and it will take "About 7 hours."

Is that reasonable?  According to the File Transfer Time Calculator at tech internets (dot) com, it should take about 8 minutes at 3.2 Gbits/sec (roughly USB 3.0 speed as I understand it).

Am I right?

4 Answers

from the spec sheet for your flash drive

132GB, 64GB, 128GB, 256GB: Write up to 15X faster than standard USB 2.0 drives (4MB/s).  This is from the "DISCLOSURES" section at the bottom of this page <>

My math says 12 hours to write 175GB.


The translation between Mbps/MBps/Gbps/GBps gets confusing to me, and adding to that the fact that theoretical maximum transfer rates are just that, I never know what to expect.

But now, about 1 1/2 hours in, Finder says I've copied about 73 GB of the total, with about 3 hours remaining.


Based on 175GB (179,200MB) and a maximum write speed of 60MB/s, it might be possible to copy in an hour, but it’s rare that users achieve the advertised write speed for a sustained transfer.

Topic starter

I didn’t clock it, but in the end I think it took about 4 to 4 1/2 hours. 

Thanks for your replies.


So much of this is dependent upon the number and size of files being moved. If it's one big file, then you might begin to see the maximum speed of the drives come into play. If it's a bunch of small files, though, then more time is spent "setting up" each copy than it is actually doing the data transfer itself.

The old file needs to be read, then the new file needs to be created on the destination, added to the directory, allocated, etc., and then the data can be transferred.