Firstly, you need to get an approximate estimate of your upload speed by using a testing site such testmy, ozspeedtest or mybroadband.
Now you need to know the size of file something you should be able to get from windows explorer.
I went to this site here and got some approximate speed estimate.
Here are my results for:
1 Gigabyte file on a 1. 544Mbps takes one Hr 32 minutes.
3 Gigabyte file on a 1. 544Mbps takes 4 hours 38 minutes.
5 Gigabyte file on a 1. 544Mbps takes 7 hours 43 minutes.
This is why few people wait for a backup to be done if they use cloud. What they do is set it up and go home.
If you are at say 1Mbps just add another 1/3 to these figures or get your own figures.
However, this should be considered to being an ideal figure as there are still other several factors to consider.
The speed of your Internet will vary greatly, and so these speeds are only a rough guide. They also do not take into account overhead; your system does not only transmit your file but also checking information to verify the line so you can add another 15%.
The more files you are backing up, the longer preparation time that is required for each one. One point one of my competitors has not picked up on is that they are backing up too many files so slowing down the backup unnecessarily.
Few people can afford high-grade commercial on the Internet because of the cost which was something that Turnbull correctly pointed out was a fraud in the proposed NBN in the debate during the last election. As such your backup over the hours will probably be interrupted and will need to resume. This will slow you down more. It will also give you misleading figures as most backup software says it's six hours the backup. It will start 10 minutes of six hours, then 15 minutes of six hours and so on, but if it falls over say after two hours, it now needs four hours more to complete and shows 10 minutes of 4 hours, then 15 minutes of 4 hours and so on. If it fell over after another 30 minutes, it would now start to show 10 minutes of 3.5 hours, then 15 minutes of 3.5 hours and so on. If you looked at it, then you would think it was only 3.5 hours to do the backup. I have had people fooled by that.
Furthermore, your Internet speed varies greatly depending how many people are using it at that exact time, sometimes they drop to a small percentage of their rated speed. For example, in my area at home the Internet speed at 6:00pm goes right down and does not shots up again until about 1:00am. Then I get a good speed until about 8:00am.
If your computer or networks are being used by other processes, the backup time will be increased. Many people have their computers doing anti-virus sweeps, communication between them and suppliers, program updates, etc.
Lastly and this cannot be stressed too highly many cloud backup solutions, have limits and slow down your backups if you back up too much in a month. They may say that give you 30 GB but in practice, it is so slow that it is unusable. You need to check this before deciding on a cloud backup.