Its not the length of the column that matters. Check the DBC (dynamic binding capacity) of the resin you are using and check the concentration of the protein in the solution you want to purify. It will give you a rough estimate on how much volume (ml) of the sample you can load on the resin (ml pi*r2*h)

I agree with Priyanka, it totally depends on the capacity of the resin being used. 1ml of CNBr Sepharose 4B is has1-2mg/ml antibody coupling capacity. 

I agree with both Ahmad and Priyanka, your column capacity depends on the volume of your column, not only its length.

In my personal experience with ConA resin, its capacity was about 2 mg of my protein per ml of packed resin. Be carefull that the binding/elution processes are slow, so do not hesitate to leave your extract/elution buffer in contact with the resin for a long time (several minutes to hours). In my case I obtained the best yeald using batch methods instead of packed columns. Of course this is strongly target dependant, you will have to see how your own protein behave.