I drink about 64 ounces or four 16 ounce glasses of veggie juice of which 32 ounces are greens a day on a juice fast. I'll throw in another 16 ounces of raw fruit juice or so in addition. And I drink even more water than that, with a couple cups of herbal teas thrown in.
I don't believe there is any set juice amount for anyone unless a Naturopath prescribes a specific raw juice diet for specific reasons. I think one should drink as much juice as their body cries for. For some that would be more than for others.
It takes approx
4 to 5 carrots
2 med apples
1 Celery stalk
1 quarter beet
and handfuls of greens such as wheatgrass, spinach, brocolli, etc.,