NIT Trichy has 45 seats in open/general category.

Some students every year are not able/willing to join NIT Trichy due to their respective reasons or some of them are not from Open Category.

So on a safer side under 50 AIR rank in NIMCET can guarantee you a seat in NIT Trichy for sure. This number can also reach upto 55 but that's not happening every year.

Simply just keep your target under 50.

All The Best.