Performance in Class XII (or equivalent) Board examination

One of the criteria for admission to IITs and ISM is that the candidate should satisfy at least one of these two criteria:

He/she is within the category-wise top 20 percentile of successful candidates in his/her respective Class XII (or equivalent) Board examination.
He/she has secured 75% (for GEN or OBC-NCL) or 70% (SC, ST or PwD) of aggregate marks in the Class XII (or equivalent) Board examination.

The marks scored in the following five subjects will be considered for calculating the aggregate marks and the cut-off marks for fulfilling the top 20 percentile criterion: (1) Physics, (2) Chemistry, (3) Mathematics, (4) a language (if the candidate has taken more than one language, then the language with the higher marks will be considered), and (5) any subject other than the above four (the subject with the higher marks will be considered).
For calculation of the total marks for five subjects, if the marks awarded in a subject isNOTout of 100, then the marks will be scaled (up or down) to 100 so that the total aggregate marks is out of 500.
In case any of the subjects Physics, Chemistry, Mathematics and language are not evaluated in the final year (e.g., in a 3-year diploma course), then the marks for the same subject from the previous year will be used for calculating the top 20 percentile cut-off and percentage of aggregate marks.
Candidates who have failed in one or more subjects in the Class XII (or equivalent) examination in 2014 will have to reappear for all the subjects in 2015.
For candidates who appeared for the Class XII (or equivalent) Board examination in 2014, but reappeared in all subjects in 2015, the best of the two performances will be considered.
If a Board gives aggregate marks considering both Class XI and Class XII examinations (in the 10+2 system), then only the Class XII marks will be considered. If a Board gives aggregate marks considering the results of all three years of a 3-year diploma or courses of equivalent duration, then only the marks scored in the final year will be considered. Similarly, for Boards which follow a semester system, the marks scored in the final two semesters will be considered.
If a Board does not give marks scored in individual subjects but gives only the aggregate marks, then the aggregate marks given by the Board will be considered as such.
If a Board awards only letter grades without providing an equivalent percentage of marks on the grade sheet, the candidate should obtain a certificate in the prescribed format from the Board specifying the equivalent marks and submit it at the time of online acceptance of the allocated seat. In case such a certificate is not provided, the decision taken by the Joint Implementation Committee of JEE (Advanced) 2015 will be final.
The criteria, as specified here, is applicable "in toto" to all the candidates including foreign nationals.

Regarding the cut-off marks for the Top 20 percentile

The category-wise cut-off marks for the top 20 percentile are calculated based on the marks scored by all the “successful” candidates in their respective boards.
The cut-off marks for PwD candidates will be the same as the lowest of the cut-off marks for GEN, OBC-NCL, SC and ST categories.
The top 20 percentile cut-off marks of the respective Boards in 2014 will be considered for candidates who passed the Class XII (or equivalent) examination in 2014, provided the candidate does not reappear for the Class XII (or equivalent) examination in 2015 in any of the subjects.
The top 20 percentile cut-off marks of the respective Boards in 2015 will be considered for candidates who pass the Class XII (or equivalent) examination in 2015.
In case a Board does not provide information about the cut-off for the top 20 percentile, the candidate will have to produce a certificate from the respective Board stating that he/she falls within the top 20 percentile of successful candidates. If the candidate fails to do so, then the cut-off mrks for the CBSE will be used.

Regarding the aggregate marks of 75% (or 70%)

The marks scored by a candidate in the 2014 Class XII (or equivalent) Board examination will be considered provided the candidate does not reappear for the Class XII (or equivalent) examination in 2015 in any of the subjects.
The marks scored by a candidate in the 2015 Class XII (or equivalent) Board examination will be considered for candidates who pass the Class XII examination in 2015.