JEE is the only exam through which you can get admission in IITs as these are governmental institutions.For JEE,you must have scored at least 75% in the core subjects(physics,chemistry,maths).JEE exams are at two levels,first the mains level and second the advanced level.After clearing advanve level,you will be called for counselling of colleges,if you have scored very well then you have chances that you will get admission in IITs otherwise NITs are provided for admission.Hope this helps you.Thank you. 

Hiii

For getting admission into IITs engineering courses, The basic eligibility is that you must have qualified class 12th exam with 75% scores with subjects Physics, chemistry and mathematics.
If you fulfill this eligibility then come the next step, JEE exams. First you need to qualify JEE mains with top ranks and be selected for jee advance.
Then you have to qualify JEE Advance with required cutoff marks. Then only will you be able to get into IITs.
There is no other exam which can get you admission to IITs. JEE main and advance is the only way out.

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For undergraduate programs at IIT there in total two Ways.

one is to appear for JEE mains qualify it and then appear for JEE advanced in get a good rank and then take admission into IIT based upon your ring you will be given branch in IIT apart from this you can appear for UCEED and then take admission into Bachelor of design course offered by IIT Guwahati and IIT Bombay.