The amount of time it takes for you to upload your files depends on two factors:
1. Your connection speed, and
2. How much data you want to upload.
Keep in mind that you can always set the maximum bandwidth dedicated to data upload by following the instructions in this article.
Determine your connection speed
There are several excellent free resources for testing your connection speed - if you input the search term "internet speed test" in an in-browser Google search, the first result is a simple speed test. Just click the blue button that says run speed test and it will run from within your browser window.
Remember - speed tests are performed in units of "bps", which is short for "bits per second." Hopefully your connection is fast enough that the results will be in terms of "Mbps", or "megabits per second." The key is understanding that your files are stored in "bytes" - and there are 8 bits in one byte. So, if your upload speed is 8 Mbps, you can upload 1 MB per second.
Determine how much data you want to upload
Find the total size of the data in a folder you want to upload by...
On Mac: right-click on the folder, select "Get Info", and look for the "Size" field in the results screen.
On Windows: right-click on the folder, select "Properties", and look for the "Folder Size" field in the results.
Divide the amount of data you want to upload by the speed, and convert to a readable time unit
Here is an example of how to make this calculation. Let's say your connection speed is 21 Mbps and your folder to backup/upload is 53 GB....
First convert your speed to bits/second.
21 Mbps = 21 x 1024^2 bps = 22020096 bps
Then covert your data to bits.
53GB = 53 x 1024^3 bytes = 56908316672 bytes
56908316672 bytes = 56908316672 x 8 bits = 455266533376 bits
So, you've got 455266533376 bits to upload at a rate of 22020096 bits per second. Dividing bits by bits per second to determine the duration in seconds...
455266533376 bits / 22020096 bps = 20675.047619 seconds
Lastly, convert your seconds into a more easily readable time unit. Since there are 60 seconds in a minute and 60 minutes in an hour...
20675 s = 20675/(60 x 60) = 5.75 hours