Do you know? you can go to
speedtest.net what is your download speed, then go to
download-time.com and enter your download speed and click any size of file to calculate how long does it take to download.
Speedtest will show you how fast your download speed is at the moment you run it. However when going out and downloading any type if file from a site you are also limited to how fast that sites server is uploading that file to you. You may be also restricted a bit by your DNS