Hi

No, your 10th marks doesn't matter at all for getting admission in IIT NIT IIIT and bits.

Also,

Your 12th marks matters a little a bit as it helps you in making you eligible for admission in IIT NIT IIIT and bits

For example,

To be eligible for IITs,IIITs ,NITs, IIITs, CFTIs one needs at least 75% marks in class 12th if belongs to General or OBC category or or at least 65% marks in class 12th if belongs to Sc or St category. For this year i. e 2021 this minimum percentage requirement of 75% - 65 % has been lifted off.

So,  if you have 75% in your 12th board examination and belongs to general category then you don't need to worry at all as you are eligible for admission in IIT NIT IIIT. If you are going to take admission in 2021 i. e this year then you don't even need to have 75% , you just must have passed 12th board examination as this minimum percentage barrier has been lifted off for this year.

Coming to BITs,

To be eligible,

you should be either appearing for 12th board examination 2021 or should have passed it in 2020 with PCM i. e physics chemistry and mathematics  (or PCB i. e physics ,chemistry and biology in case of students applying for B Pharma, PCM candidates are also eligible for B Pharma)

=) You should have got at least 75% marks in aggregate of physics chemistry  and mathematics ( if you have taken mathematics for your BITSAT examination)

or

at least 75% marks in aggregate of physics chemistry  and biology( if you have taken biology for your BITSAT examination)

=) you must have got at least 60% marks individually in each of physics, chemistry  Maths/ biology

You can check detailed information regarding eligibility at

https://engineering.careers360.com/articles/bitsat-eligibility-criteria/amp

So, 10th marks doesn't matter at all ,while 12th marks is required to make you eligible  but admission is completely based on the rank obtained by you in entrance examination that  is

• JEE advanced in case of IIT
• JEE main in case of IIIt, nit
• and BITSAT in case of bits

Thank you