Hello Ashutosh, Top 20 percentile of any board for that year will be released after the Results will be released, So, Top 20 percentile for 2020 will be released after the results of board are announced, Moreover, Top 20 percentile of any board is calculated by marks scored in five subjects which are

Physics

Chemistry

Mathematics

Language subject

Any subject other than physics, chemistry, Maths, language paper

If any body has taken 2 language paper then higher marks scored subject will be taken for calculating top 20 percentile.


Now Top 20 percentile of Bihar board for last three years(marks out of 500)

2017

General Category - 313
OBC NCL - 307
SC Candidate - 300
ST Candidate - 303


2018

General Category - 293
OBC NCL - 287
SC Category - 279
ST Category - 284

2019

General Category - 346
OBC NCL Candidate - 347
SC category - 332
ST Category - 339