If you are somehow not specific on what branch, then a rank up to 22,000 (other states) can be expected to safely accomplish a branch at IIEST, Shibpur. You require to obtain marks of about 150 - 160 in JEE Mains for that.

For home-state students, the closing cutoff is usually around 30000 in general. 

Cutoff: 

The recent cutoff trends at the institute are tabulated below.

My cousin’s JEE-Main score was 142, and the normalized score was 175. Since there is no normalization nowadays, a suggestion would be to work hard for the score. 

And, a score anywhere between 180 would give you a position in the stream of your choice, you can be confident about that. Hope this gave you an idea about the score required to take admission at IIEST Shibpur.