The value depends somewhat on the type of supply, but here's a rule of thumb that I've found useful for a simple full wave rectifier with a capacitor input filter:
C = 10/(2*Pi*f*R)
will yield 10% ripple and 10% regulation (no load to full load). The values scale roughly linearly over a range of about 4:1.
Units:
C Farads
f Hertz
R Ohms
This rule gives a good starting point. In your case, the result is 8800 µF. Double the capacitance yields half the ripple, half the regulation %.
I hope this helps.