how is 50th percentile is calculated

50th percentage of the highest mark

 Percentile is calculated by taking the product of your marks x 100 and divide this product by the highest mark obtained by the top ranker.
This is how you calculate your percentile based on the marks.
This is subject to variation since none of us know how much will be the highest marks.

Hi Saibal,

The percentile is calculated on the basis of score of that year. The percentile are calculated with formulae-

(Your Score/Highest score in the examination)x100

The 50th percentile are qualifying marks decided by CBSE. A candidate has to score minimum 50th percentile for qualifying in the examination on the basis of which ranks will be decided.

All the best!!