Hello aspirant, 

If you have passed class 12 having percentage above 75% and are in top 20 percentile in class 12 examination conducted by respective boards,then you are eligible to give jee mains but you want to give jee advanced you should must have 75% in PCM then you will only allowed to sit in the examination. 

Hope this helps you. 

Good luck. 

Hello Raunak Singhi....

There is no defined criteria because if you think for iit/nit/iiit then you are more or equal to 75% or top 20 % in respective boards but if you think for private college atleast your % should be more than 65%  .

If you want to enroll yourself in an engineering college then there is no such criteria for your pcm score,but make a target of atleast 70-80% marks ,and if you want to get good college focus on good score and pursue engineering from a good college.

All the best

Thank you