I would like to tell you about the No of Seats, eligibility as well as Number of attempts in IES Exam, as you want.

It's different for different branch,
Civil :
it varies from 150 to 280 depending on vacancies in different department.

Mechanical
100 to 150

Electrical
100 to 125u

Electrical and electronics
100 to 125

Total number of seats varies every year


Number of UPSC IES Vacancies:
2014: in the year 2014,
The total number of vacancy are 582

2013: in the year 2013,
The total number of vacancy was 763

2012: in the year 2012,
The total number of vacancy was 560

2011: in the year 2011,
The total number of vacancy was 693

2010: in the year 2010,
The total number of vacancy was 434.

IES exam is conducted by UPSC in once time in year.

If Applicants have completed engineering discipline in following departments then Applicants are eligible for IES exam
Civil Engineering

Electrical Engineering

Mechanical engineering

Electronics and Communication Engineering

The Applicants age should between 21 yrs to 30 yrs.

Age relaxation is provide for SC/ST/OBC Applicants.

Final year Applicants also eligible for IES exam .

Number of attempts for IES exam is
For general Applicants it is 4.

And for OBC Applicants it is 7 times.

And for SC/ST Applicants it is 9 time