Hello dear student !
IHM is one of the renowned institutes of India. The ranking you need to get selected in IHM depends on your category (General /OBC/SC/ST) . If you comes under General catagory, then you need to secure a rank between 15-400 for best colleges which basically includes IHM Mumbai, Banglore and Pusa. If you are from OBC catagory, then you can get admission with rank till 1800 for Pusa , 5000 for Mumbai as well as 9000 for IHM Banglore. Rest the cut off changes every year.
Hope this will help you