Hello dear, 

In order to take admission in IIMs, the students must clear, 

1) common admission test (CAT) 

2) Written ability test ( WAT) And personal interview (PI) 

Most IIMs take admission on the basis of CAT and PI. The cut off percentile differs from IIM to IIM. 

Please visit the link below for percentile cut off of IIMs: 

https://bschool.careers360.com/articles/iim-admission-criteria-2018-20?amp

All the best!