You have to score around 860 marks+ in gate to get a rank below 50 in it.Below are the cutoff trend of various institutes:

• GATE 2017 Cutoff for Chemical Engineering for various institutes

Name of the Institute
General
OBC
SC
ST
PwD
Gen Pwd
OBC PwD
IIT BHU
470
431
324
208
-
-

IIT Madras
582
573
384
242


199
IIT Delhi Direct Admission
670
630
535
445
535


IIT Delhi -Interview and Shortlisting
540
450
375
300
375

• GATE Cutoff 2015 for Chemical Engineering for various institutes

Name of the Institute
General
OBC
SC
ST
PwD
IIT Kharagpur
572
509
441
358
211
IIT Bombay
600
540
400
400

A score of 870+  shall fetch you ranks below 50 innGATE examination as per trends.
With this you have decent chnaces for MTech CSE at IIT Bombay and Madras.
The cutoffs at top institutions go down to 770 for top branches in demand like Aerospace Engineering, Mechanical engineering and CSE.
Your GATE scores shall be valid for three years.

For Chemical Engineering, a score of 650-700 can fetch you top colleges.

Dear Roy
I too agree with Mayank. If you get more than 800 only there are some chances to get into below 50 rank but sometimes it might change due to competition. Please go through the below link for more more details.
Click here
All the best.

Graduate Aptitude Test in Engineering

Eligibility | Application | Exam Pattern | Admit Card | Preparation Tips | Books | Question Paper | Accepting Colleges

Get Updates Brochure