OneDrive for Business Client Network Bandwidth Calculator

There is now official guidane here: https://docs.microsoft.com/en-us/onedrive/network-utilization-planning

There is also a Microsoft tool on GitHub that may help (I've not used it before)

/Office 365 Network Bandwidth meter/
This is a beta solution we released recently in September 2018 to:
1, Measure network bandwidth usage for pilot users on-boarded to Office 365 or network bandwidth usage of on-premises users.
2, Build and maintain endpoint monitoring dashboards post on-boarding users to Office 365
This solution uses Azure monitoring, specifically Service Map. You can apply this concept for measuring any SaaS/PaaS traffic, not just Office 365.

https://github.com/microsoft/Office365NetworkTools