For grown chickens (in this case mom) allow 4 sq feet indoor (coop) and outside 10 sq feet space and for chicks brooder space:
up to 2 weeks: 0.5 sq ft per chick
2-4 weeks: 1 sq ft per chick
4-8 weeks: 2.5 sq ft per chick
over 8 weeks: 4 sq ft per chick