chicken management
stocking density
Stocking density refers to how many chickens can be kept in a given area in relative comfort and harmony.

minimum space requirements
The minimum space required to keep  chickens in a healthy and happy state varies depending on :-
  1. The size of the chickens.
    EG bantam chickens need less space than large meat chickens.
  2. The age of the chickens
    Chicks and juvenile chickens need less space than adult chickens.
  3. Whether the chicken numbers remain static or fluctuate throughout the year.
    If you let hens raise broods of chicks with the intention of eating the chicks when they reach adulthood your flock may swell to as much as three times the size of the regular flock in the interim before all the chickens raised for meat are eaten.
Photo of chickens in a deep litter pen
My chickens waiting to be let out of their deep litter run in the morning.  On the left of the photo is the edge of their coop which has a hatchway that directly connects to the deep litter run.
As well different publications and websites on keeping chickens give conflicting minimum space figures.  In an attempt to simplify the formula I have come up with these figures based on the averages of a number of these sites:-
  1. Perch length              25 cm (10")
  2. Coop space               1.2  m²  (4 ft ² )
  3. Outdoor run space   1.2 m² (4 ft ² )
These figures are for mid sized utility chickens.  If your are running layers or bantam chickens you could probably reduce these chicken to area ratios by 20%. 

Also note that these are minimum space requirements, ideally it would be better if you had more space per chicken than these minimum figures.

the space chicken ratio for my chicken run
It is difficult to directly compare my chicken run with these figures as I have a deep litter run attached to the coop.  While my coop is relatively small the chickens have access to this deep litter run at all times, plus part of this run is under cover and extra perch space can (and has in the past) be added in this section.  For this reason I count both my coop and deep litter run as a single space when comparing with the above general space ratios.

As well the number of chickens housed in the run has varied over the years.  These days I usually only run about six chickens using the Staggered Replacement System, however in the past it housed anything up to eighteen chickens.  But these high numbers were seasonal as they were when I was raising young chickens for meat.  During the Summer the numbers would be high but by the following winter the figure would be back down to six to eight. 

Below is a graph showing the total area of my chicken run plus the space per chicken.  For simplicity this graph only shows metric figures.
6 12 18
Perch length 5.4 m 90 cm 45 cm 30 cm
Coop/Deep Litter run 18.4 m² 3.5 m² 1.5 m² 1 m²
Main Run 44.4 m² 7.4 m² 3.7 m² 2.5 m²
(only limited access) Extended Run 146 m² 24.3 m² 12.2 m² 8.1 m²

Other factors to consider
It is not just space that affects the well being of your chickens.  Below are five other factors to consider.
  1. Shade
    Photo of a hen under a shady tree
    Barnevelder hen in the shade of a cherry tree.  It is important that your chickens have access to a shady place, especially in hot weather.

    Photo of chickens walking on boggy ground.
    What you don't want is to have your chickens walking around on boggy ground.
    Chickens like plenty of shade so they can get out of the glaring sun in the heat of the day.  If your chicken run doesn't include a tree or an overhang then I suggest you put up some shadecloth.  The coop cannot be the only shade as it will be too stuffy on a hot day.
  2. Sunlight
    Chickens also like to sun themselves, so make sure that you have at least part of the chicken run getting full sunlight in winter.
  3. Drainage
    Chickens do not like sloshing around in mud.  If your chicken run is prone to getting muddy in winter than consider putting in agricultural drainage pipes.  Another option is to mound one part of the run up so as to form a higher and hopefully drier hillock.  Adding sand to make the soil more friable will also help.
  4. Protection from the wind
    Chickens don't like cold wind.  If your chicken run is a bit of a wind tunnel then consider putting up some wind breaks.
  5. Dust baths
    Chickens love dust baths.  These can be achieved naturally by a combination of plenty of sunlight and well drained soil.   Mounding up an area and adding sand will aid in creating a good dust bath area.