Size of the Microsoft Purview Audit Log for sizing SIEM / Splunk Storage

Hi there,

we plan to export our M365 Audit Logs into a Splunk solution.

The license cost is based on the storage needed.

my questions:

- is there a way to assess the storage used by our Audit logs in Microsoft Purview?

- is there a way to calculate the storage needed for a number of users in a give time, e.g. per day/ week for heavy, medium, low M365 usage, I only need rough numbers?

- does anybody have experience or numbers of their export to a SIEM system?

Any support highly appreciated.

Thanks,
Franck