One of the most useful features in SharePoint online is the ability to maintain an offline copy of your files stored in your OneDrive or document libraries. This is done by using OneDrive for business desktop client. One of the first questions that arise when trying to deploy this feature is how to calculate the bandwidth required. Now there is a calculator released by Microsoft to estimate the bandwidth that an OneDrive for Business client deployment will require.
According to Microsoft;
“this calculator can be used to provide a loose estimate. Once you download the calculator, you will see that there is an opportunity to adjust some of the settings on the Input tab such as the user profiles, working hours, and time zones for your organization. The numbers included are what Microsoft has observed in the field. You can also adjust the number of clients per site and what profile each of those users have on the Client Mix tab.”
If you want to get more understanding of how the calculations are made, there are 3 hidden sheets you need to refer to.
Process Labs 
Excellent! Thanks for this – I've been looking at this feature for ages. Followed your instructions and it works a treat!
The link to download the calculator seems to be dead now.
Link is no longer working.