Check Office 365 Mailbox Size

Do you need to check the mailbox size in office 365?

In this guide, I’ll show you two methods to find the office 365 mailbox size.

Method 1: Find Office 365 Mailbox Size Using PowerShell

You need to have the Exchange Online PowerShell V2 Module installed. You can install this module with the command below.

Install-Module -Name ExchangeOnlineManagement

Once installed you will need to run this command to connect to Exchange Online. This command support MFA.


Get mailbox size for a single user. Change identity to the email address of the user you want to look up.

Get-Mailbox -Identity | Get-MailboxStatistics | select DisplayName,TotalItemSize, ItemCount

To find the office 365 mailbox size for all users use this command.

Get-Mailbox -ResultSize Unlimited | Get-MailboxStatistics | select DisplayName,TotalItemSize, ItemCount

You might get a warning like I did if you have any mailboxes that have not been signed into.

That is it for method 1.

Method 2: Find Office 365 Mailbox Size using Exchange Admin Center

This method only allows you to check one mailbox at a time.

Step 1: Go to the Exchange Online Admin Center

Step 2: Go to Recipients and click on any user

Mailbox usage details are displayed in the lower right.

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