How to evaluate the RCS of an array

I would like to find the RCS of a finite array. Say I have a planar array (5x5), and I want to find the monostatic RCS at broadside. Assume the element's RCS is known (say a simple dipole). What would be the total RCS of the array? Of course we can assume no mutual coupling between elements.

I guess the total RCS is proportional to the RCS of a single element and the array factor (directivity at broadside). But is there another factor for the total RCS of the array?

Thanks for the help.

The best way is to measure it. A good VNA can be used, with a calibrated antenna on the other end of radio link. You can also use a calibrated radar and an open test range. The RCS of the array under test also varies with its load impedance.

Thanks!
The purpose of doing this estimation is actually for the measurement. However, I would like to be able to understand and analyze the measured RCS.
For this test, the elements in the array are not "real" antennas, but some simple passive scatters such as half wave dipoles. All I want to know is if there is a simple rule of thrum that can tell the total RCS of the array based on the RCS of a single element.
I guess I can try to understand this from simulations.