How to estimate the required database size when database logging is turned on?

Gateway 2 - Databases
https://resources.itrsgroup.com/docs/geneos/Gateway2/databases/databases.html

2.3 Sizing
It is difficult to provide an accurate figure for the size of the database required as database sizing is affected by so many variables:
- The number of metrics stored and the interval at which these are stored
- This itself is a function of the number of managed entities monitored, plug-ins used, etc.
- The volatility of the metrics
- Housekeeping / archiving strategy

A minimal size for a database in Mbytes can be calculated using the following formula:-
Size = Number of Managed Entities * Number of months data to be stored * 10

In practice the size of the database required can be minimised by
- Keeping only a limited number of days of data
- Carefully considering what data is logged and only logging data which has a known use
- Specifying the interval at which items are logged and using margins