Capacitor Sizing in Power Supplies

I seem to recall a formula in some Gecko docs re capacitor sizing on
roll your own power supplies (the xformer, bridge, cap variety). And
I think this formula was of the form (80,000*amps)/volts = uF of cap.
(The 80,000 is related somehow to the number of millisecs per half
cycle of 60 cycle AC and the time it takes the cap to charge?)

Suppose you wanted to build a 2VDC @ 20A supply. Without getting into
why one might want to do that, this works out to 80,000*20/2 = 800k
uF. That's a lot of capacitor, albeit at pretty low voltage.

Is this a non-linear situation or would 800k be the proper sized cap?

(Mariss, if I'm misquoting you--sorry.)

Thanks in advance.

--Jack