To calculate your expected rank you can use this formula-

874469 are the number of candidates appeared for the January exam. So rank formula is (100- your total score) * 874469 / 100.

If the number of candidates for April exam increased to 1400000 then your final rank shall be (100- your total score) * 1400000/100

You can also check your admission possibility with the given below JEE Main college predictor.

https://engineering.careers360.com/jee-main-college-predictor

It is difficult to predict your exact rank as JEE Main 2019 Entrance Exam is being conducted twice in a year in multiple session first time.

Good Luck!