I’m updating the answer for a more complete an accurate one, using command, and some string operations to avoid Windows 32bits integer overflow.

　　Remember you need to run and check what is the line of your network adapter. The following batch file uses the 4th string line, that’s the 1st adapter listed.

　　It checks the speed every 10 seconds. If your upload or download speed is up to 100 MBytes per seconds, you need to repeat the loop more often (for example every 1 second).

　　It creates a .csv file too. Remove that last line if you don’t need it.

　　The batch file:

　　Keep in touch if you need a fix.

　　Previous solution using a batch file, with some limitations:

　　I wanted to give you an easier solution, then I used my previous answer to code a fresh windows batch script that iterates every 10 seconds. It monitors download and upload bandwidth/speed in console and logs ammount of bytes transferred in a .csv file.

　　PS: Windows limitations are the counter resets every 4GBytes transferred and at midnight.

　　Old solution using task scheduller and XAMPP:

　　I had to monitor and log the amount of data downloaded as your case, and found it faster to run a script with the Windows task scheduller than looking for a free software that dump the usual graphics info into a file. Perhaps my homemade script works for you.

　　I started a local Apache/PHP server using XAMPP for Windows and run this script from command line. For example:

　　The script uses @phep answer suggested windows command . You can create the script file with the notepad, and the code is:

　　Then I processed the the .csv in a spreadsheet software to calc the download speed (bandwidth) using the difference between 2 bytes values over the difference between the 2 matching time values (bytes/seconds).

　　Feel free to ask a fix to log the uploaded bytes. Wish it be useful.