I depends on what breed they are! And what time of year it is.
A chicken fed the same ration year-round will eat more during cold weather, because it needs more energy to keep its body warm.
As some extremely general guidelines, expect to feed:
Each mature bantam about 1/2 pound (0.25kg) of feed per week.
Each mature light-breed chicken about 2 pounds (1kg) of feed per week.
Each mature mid-weight dual-purpose chicken about 3 pounds ( 1.5kg) of feed per week.
Each mature heavy-breed chicken about 4 pounds (2kg) of feed per week.
Each meat bird about 10 pounds (4.5kg) of total feed to reach mature butchering age.
A chicken that doesn't get enough to eat won't grow or lay well. A chicken may eat too little if it goes through a partial or hard molt, if it's low in the peck order, if the weather turns hot, or if it finds its ration unpalatable.
If your chickens don't seem to be eating enough, perk up their appetites.Begin by feeding more frequently, even though the trough may already be full. Offer variety - chickens are particularly fond of milk, cottage cheese, yogurt, tomatoes, salad greens, and sprouts. Moistening the feed may also increase appetite: for each dozen birds, stir a little water into 1/4 pound (0.1kg) of ration fed daily. If your appetite-stimulating attempts fail, the issue may not be not be the ration but poor health.
Feed that disappears to fast is a sure sign something is wrong. Your chickens may be infested with worms. Take a sample of dropping to your vet for a fecal test, and worm your chickens as necessary. In winter rapidly disappearing feed may mean your chickens are too cold. Eliminate indoor drafts, and increase teh carbohydrates in their ration. Disappearing feed may not be your chicken's fault at all-make sure rodents, opossums, wild birds, and other creatures are not dipping their snouts into the trough!