Depends also on how heavy your chickens are/ how well they fly.
My Marans like the two foot high perches, my little bantams like the five foot high ones. I try to have landing spots so they only have to go up or down in two or three foot increments.
I greatly, greatly, enormously, recommend perches that are close to 4 inches wide so that you don't get frost bite on the toes.
I also really like poop trays (lots of threads on here about poop trays)
Other than that......
Perches should:
- Be higher than your nest boxes
- Have enough head space, for a standard size breed that is about a min. of 16 inches, but if they are flying up to the perch, then two feet.
- not have any wind blowing on the perches in the winter (but venting is very important)