Update 3-24-15: Latest Office 365 bandwidth guidance is here: https://aka.ms/tune
This is a pretty common question I get with my education customers. The answer is there is not one tool that can calculate everything for your Office 365 bandwidth but there is an Exchange calculator, Lync calculator and some guidance for SharePoint bandwidth.
Exchange bandwidth calculator
This calculator is pretty extensive as it accounts for mail usage profiles, etc:
It also allows you to calculate bandwidth needed for each site depending on what client type Mac, Outlook 2010, OWA, etc.
You can visit my other post for a bit of a deeper dive into using this bandwidth calculator here.
Grab the Exchange bandwidth calculator here.
Lync 2010 and 2013 bandwidth calculator
This is a pretty awesome bandwidth calculator where you can provide site by site calculations for Lync bandwidth required.
You can specify locations, users, type of users, concurrency, etc.
Lync calculator also has nice graphics showing bandwidth requirements per location, etc.
Grab the Lync bandwidth calculator here.
I haven’t found a calculator on this for SharePoint 2013 but I did find a reference matrix from SharePoint 2010 which should be enough for a baseline estimate for SharePoint Online – I did read that SharePoint 2013 bandwidth can be up to 40% more efficient than the results below so take that into account in your estimations:
Here is an Office 365 WAN test result on SharePoint 2013 that has great information but not customer guidance unfortunately. See here.
There are other older SharePoint calculations available for reference here.
You can also view your available network bandwidth by running the Office 365 bandwidth test tool which is available here.