According to the available information, the NIFT eligibility standards are 10+2 from a recognized board or university as per Indian Law. However they don't specify a percentage, hence there is no minimum percentage requirement. Your grade in the Class 12th board exams has no bearing on your NIFT score. Admission to NIFT is solely based on how well you perform on the NIFT entrance exam. But to be on the safer side and for your unhindered academic future and career, it is important that you must keep your 12th percentage at or above 50.
Now, the question of percentage might come up if you are going for the B.F.Tech program or M.F.Tech there are certain requirements like you must have Physics, Chemistry, and Mathematics, with the required passing aggregate.
Therefore, different course programs have different pre-requisites, which you must check out.
For any latest updates, you may visit the Official Website of NIFT.