is 70% plus in 12th boards enough to give iit jee or do i need 80%

Getting higher precentage in 10+2 don't have much of effect on whether you would get into IIT or not as 10+2 has nothing to do with getting admission in IIT as it totally depends how you perform in IIT-JEE but still you need to get at least 60% in 10+2 and will be much better if you get to 70%.

Best Of Luck!