how voracious are chickens?

[drewder]

I've got about an acre and a half of grass and I'm curious how many chickens I could have free roaming and grazing and still have grass?

 

[oldhenlikesdogs]

They don't actually mow the grass down, once it gets taller than a few inches they ignore it, they eat a little bit of grass and weed leaves, but they are mostly after seeds and bugs, so your grass would grow pretty tall.

 

[aart]

I've got about an acre and a half of grass and I'm curious how many chickens I could have free roaming and grazing and still have grass?

As far as I know there's no pat answer to this question.
There are a lot of variables including what kind of grass/vegetation you have growing in the area.

The combo of the bird scratching and the accumulation of poop can decimate plant life.
There will always be areas that they scratch big holes in and areas that remain growing just fine.

Is this your 'yard' or a pasture area?
How many birds do you want...what are your goals and main concerns?