If you need to calculate your “SAP client Size” then you can easily use SCCL (SAP Client Copy Local) transaction or SAP program RSSPACECHECK for this issue..

METHOD – 1 SCCL

Go to transaction SCCL on target client and choose the “Source Client” with “Test Run” option

* Source Client is , which is you want to calculate

Continue with “Schedule as Background Job” or “Start Immediately” options.

If your source client size is big then my suggestion is choose the “Schedule as Background Job” option.

Click the “Continue” button

Continue with “Resource Check” button

When action is completed then you can see the following screen and this screen shows the size of your client…

 METHOD – 2 RSSPACECHECK

Go to transaction code SE38 and execute the program RSSPACECHECK

Choose the “Client Number” which you want to determine and insert “*”  sign for the “Table Name” area

F8 – Execute

After some time depends on your client size , you will get the result like shown below.