Dear Cauvery85,
Welcome to CiteHr.com!
Can you give the reason why you want to know?
The recent controversy by PSUs was due to the fact that it was difficult for them to place the candidates as per their "seniority" since percentages offer a 'ratio scale' for measurements. However, considering the fact that a typical engineering or management course has about 40 to 60 courses, each course having several components of evaluations such as mid-term and final exams, assignments, projects, etc., does a single percentage system truly reflect the composite differences between many candidates?
By the way, there can be no standard formula for such conversion as different institutes adopt different criteria.
Warm regards.