Figure on about 9 lbs per day for your flock, at about 4 oz per bird per day. On average. For the average-size hen.
I don't fill a feeder during the squirrel times of the year....most of it! So I scatter food twice a day. I throw food and wait for them to eat it, until some of the hens start to walk away. Then the ones lower on the pecking order come to eat. Make sure everyone gets to eat if you feed this way. It works well for me.