Apply the proper derating factors to the connected load.

If you list and describe the connected loads, perhaps we can help further.

As an engineer, it is up to you to determine what loads will be energized at the same time to arrive at the demand load.

Plot a graph with time in X axis and Current or VA in Y axis at 15minute intervals and see.
More useful method is to connect a data logger/power analyser to the main CB and record I,V,pf,Hz,VA,W,VAR, harmonics etc for a 24hr period.

Data loggers only work if the building is already built and in operation.

A graph may work if the engineer consults with the end user to determine how the loads will be utilized.