Hi , I am planning to install a 100 amp subpanel in my basement , I am adding about 1200 sqft of finished space in my basement. My current panel is a bit full so I want to add a 100Amp Sub Panel, going to have around 22 recessed lights, ejector pump circuit, Dehumidifier Circuit, sink pump circuit, outlets.
I currently have a 200 amp service. I have only 4 open slots in the 200 amp main panel .there are two 30 amp circuits for the central air units, in the panel now and one 40amp for the electric Oven.
I would like to know if I can add this much to the total load that will be placed on my main panel?
Also I plan to use #4 wire to feed the subpanel ,the panels will be within 20 feet of each other.

One hundred amps seems like over kill to me. I'd use a 60 amp panel with #6 Romex and a 50 amp breaker in the main panel. Number 6 Romex is limited to 55 amps. That gives you 50 amps at 240 volts, 100 amps at 120 volts. More than you need and leaves plenty of room for expansion.