Hi Ranajit, 

The rank calculation depends on the total number of aspirants who took the exam. This year the total number was 874469. Thetefore, the formula for calculation of rank will be (100-Your Percebtile) x 874469/100. Accordingly your predicted rank will be approximately 444,929. 

For more on rank prediction, read up the following links given below.https://engineering.careers360.com/jee-main-rank-predictor?utm_source=google-search&utm_medium=paid&utm_campaign=jeemain-rp