Hey!There

It depends upon level of paper and stream in which you are interested..There are various stream in IIT BOMBAY from CSE to biotechnology.You need 200+ for IIT BOMABY.But if you are looking for core stream then you need 250+ under General category..

Ask if you have query..

GOOD LUCK!

Dear Shivam, it depends on the question paper and the number of  students who are giving exam. Since IIT Bombay is one of the top IITs so, your AIR must be under 70 to get your preferred branch. This rank approximately corresponds to 275+ score.

If you belong to reserved categories then - 

For obc upto 180 to 200

For sc upto 400 to 500

For st upto 1500 to 1800.

It is just a approximation .

Getting to IIT depends on the question paper. 

All the best 

Hope this helps