1/10th as much as a champagne will eat if you give them truly free choice pellets. :lol: They are serious bottomless pits but they expend very little energy for their size. What little energy they expend is generally getting themselves in trouble. I had a pair of does in my first colony get to a bag of pellets and make 20lbs disappear somehow before they were checked the next day. That's more than the weight of the 2 rabbits. :? Another time they got the feed bucket down and ate 2lbs overnight plus their allotted scoop.
First check your pellet bag to see if it has a suggested starting place for your feed. It will also depend on how far grown they are and pregnancy. Then you take into account anything else you are feeding like hay. Kent pellets suggest around 8oz for a large breed. Manna pro actually says to free feed all rabbits unless they need restricted which most rabbits not raising a litter will. Hay will help fill them up so they don't need meals as often since rabbits are not really designed to only have food for a short period of the day. With our large rabbits we were mostly free feeding in colony and alternating a feeder full of pellets with a feeder full of straight grains for the caged rabbits. All with hay. I actually had trouble with my rabbits not being bulky enough even on a lot of pellets because most spent majority of their time in colony and had more of a sleek muscled appearance that didn't go over well on the table.