On its Summary tab, you can easily switch between local and cloud, and get estimates on the required hardware and (cloud) storage. The Input Sheet allows you to enter specifics for the organization. It comes in the form of a Microsoft Excel file. The German Backup Bros Benedikt Däumling and Christian Stein have created a Veeam Backup for Microsoft Office 365 Calculator. Use the latest Veeam Backup for Office 365 Calculator Excel sheet The online capacity calculator was originally the work of Veeam’s Senior Solution Architect Hal Yaman, but has since seen a lot of improvements. As a bonus, the online capacity calculator will even provide you with pricing information for object storage in Microsoft Azure. You can clearly distinguish the efficiency of object storage in the online capacity calculator when comparing to a disk repository. The online capacity calculator allows you to sign in with admin credentials of a Microsoft 365 tenant, but you can also manually enter values. On the Veeam website, there is an online capacity calculator website for Veeam Backup for Office 365. Veeam Backup for Microsoft Office 365 Capacity Calculator

Use the Measure-VBOOrganizationFullBackupSize PowerShell cmdlet.

Use the latest Veeam Backup for Office 365 Calculator Excel sheet.

Veeam Backup for Microsoft Office 365 Capacity Calculator.

There are, actually, three good ways to make a guesstimate on the required disk space to store the repository, whether it's on disk or in object storage:

As organizations embrace the full suite of Office 365 and intend to use Veeam Backup for Microsoft Office 365, I often get the question on how to properly size the storage for the repository for Office 365 backups.

Veeam backup storage calculator