Are you talking about using it for a nest box or for a coop? Nest boxes need to be at least 12 x 12" for individual boxes, and some folks build a community box that is much bigger, intended for multiple hens to use at once. If you are talking about using it for a coop: absolute minimum size recommended is 4 sq. ft. per bird. Your cage is 12.5 s.f. While technically, it is big enough in sq. footage, it is not big enough to allow them to perch. I predict that if you try to keep them in that for a coop, you are going to have lots of behavioral issues. More info needed to answer you adequately. Is this to be their main and only living space? Do you have a run?