how to calculate the real depth?

hi,
I am confusing about how can i calculate the real depth, i use the formula d = ( float(p) - 1. ) / 256. that mentioned in cityscapesscript to calculate the disparity value , and then i calculate the depth using : depth = baseline * focal length / disparity value , for example: depth = 0.22*2262/0.13=3828. i got a very large depth value, is that correct? how can i get a correct real depth?