Hi Diptesh,

Hope you are doing well. Coming to your question... 150 marks is your raw score i.e. the marks you have received. While on the other hand, a percentile is a measure that indicates the value below which a given percentage of observations in a group of observations fall.

For example: 90 percentile means a value below which 90% of observations fall. In short if someone got 90 percentile, it actually means that if 100 students had given the exam, 90 students scored less than him.

There is definitely a process to calculate percentiles but for that only raw score doesn't help. In realty when someone says 150 marks means "x" percentile, it is said based on historic data.

Hope this helps.