Hi Jim,
Thanks for posting in the community. We are happy to help you.
This depends on the plan type and the number of plans you have purchased. Please allow me to explain.
For most plans, each license adds 10 GB quota for total tenant storage (SharePoint only).
For your reference:
Let's assume that you have purchased 10 "SharePoint Plan 1" and have assigned them to users. In this case, your organization has increased 10 x 10 GB =100 GB of space at a cost of $50/month. Therefore, your cost is $50/100 = $0.5/GB/month. Also, your current total tenant storage (SharePoint only) should be 1 TB + 100 GB = 1124 GB (1.0976 TB). Note that The 1 TB is the default tenant quota, not the plan quota.
Additionally, here is the situation in my test tenant. I have 20 "E5 plan" and 2 "E3 plan". Therefore, my total tenant storage (SharePoint) is 1 TB + 22 x 10 GB = 1244 GB. I have run the Self-help diagnostic for "SharePoint Tenant Storage" and the calculation is correct.
![Image](https://learn-attachment.microsoft.com/api/attachments/38ac1310-869a-417b-bd46-640f3f9c76e5?platform=QnA"https://learn.microsoft.com/en-us/microsoft-365/commerce/add-storage-space?view=o365-worldwide" title="learn.microsoft.com" rel="ugc nofollow">the Office 365 Extra File Storage add-on" to add more storage, then the cost will change.
We look forward to your response. Thanks for your cooperation.
Sincerely,
George | Microsoft Community Moderator