Hello.
Percentile is calculated on the basis of the number of student who get marks equal to and less than your marks it is even quite difficult to predict marks from percentile directly, it may become easy if you know that how many student get marks equal to and less than your marks and the data is not disclosed for everyone and even the data is very vast that may be the another reason, generally the percentile calculation vary according to the number of student appeared for the exam, if it is about 90 percentile then it looks that you have good percentile but in actual not, here the difference in percentage and percentile is that higher the number of percentage designate that you actually have a good score but higher the number of percentile not necessarily designate that you have good score it depends upon the number of candidate appeared for the exam, difficulty level of the exam, percentile scored by the toppers.
Best of luck.