perch space

 Hi,   My chicken house is assembled and I am going for my chickens on Saturday. How much perch space do I need to allow for each chicken?   The house was advertised as 8/10 hens but I am thinking more of 4 for comfort.

Thank you, so  will be o.k. with 4.  As as far as the run goes we are building a large run for them cannot remember the measurements but it is big and we have several places to move it too.  I would love them to be free range but I have nearly half of an acre surrounded with hedgerows and it would cost a fortune to put fencing around so they could not get out and of course we get the foxes and I grow veg and have flowers.