How to decide size of column in a building?

The size of the column depends on the load of the column that is lateral loads and axial load. Generally we design the column by using Etabs or Staad pro
These are the following steps to decide the size of the column:
As we already discussed that the column size depends on the load of the column, then the calculation of the total load like dead load, live load seismic load and wind load is taken into consideration.
Dead load is generally the self weight of the structure.
Live load is a moving load or difference for the commercial and residential area.
The live load of residential building is 250kg/mm²
The live load of commercial building is 400kg/mm²
Whenever the total load is calculated then it is easy to consider the size or type of the slab.
After identifying the type and size of the slab, the load which is transferred on the slab to the beam is found out and then size of the beam is identified
The loads on beams are calculated then the load is transferred from beam to the column is calculated by moment distribution method.

After identifying all the parameters mentioned above, the engineer needs to take help from recommended software like E-Tabs, STAAD Pro etc. to recognise the model and to examine the behaviour of the structure under the different types of loading patterns.