Excuse us. For a VSI, you calculate the C so that maximum motor current can be delivered without causing too much voltage ripple. How much is too much? That is one of the parameters you have to decide on. Something like 10% ripple at full load is a reasonable value. But some want less and some Think that more is OK.
For an CSI, you need to design the inductor so current ripple at full load is within set limits. Ten percent is a common value if nothing says otherwise.
There are models available at simulator companies that make the job easier and take a lot of circumstances into consideration.
You also need to ensure that the ripple current rating of the capacitors is sufficient for the application.
Sometimes, the selection may be on ripple current rather than just capacitance.
