Basically, you may refer to this SAP Note 1518419 – Page file and virtual memory required by the SAP system to determine the page file size required for SAP system.
The page file size required for your SAP system depends on the available RAM of the host and varies according to the number of SAP instances you install on your host.
From the SAP Note 1518419, you will find an attached Microsoft Excel sheet to calculate the page file of an SAP standard configuration.
