I've got 4, ten week old pullets. On average, how much feed will they eat in a day? They free range a few hours in the afternoon, and I give them some treats too.
I can say that I never let any of my chickens feeders go empty. They get food 24/7, on top of free ranging. I'd suggest buying a 20-25 lb. bag and tracking it. Once they start laying, gradually switch them to layer, usually 18-24 weeks of age. By then they will be eating more and you can get the 50 lb. bags. The key is to keep feed clean, dry and bug free. I use 30 gallon, galvanized trash cans.