The Iranian grading system is similar to that of France's in secondary schools and universities; the passing grade is 10. Graduate programs require 12 and 14 as passing grades for Master's and Ph.D. level programs, respectively. Iranian grades are not convertible to the 4.0 scale GPA directly, and should be used according to the destination universities' regulations. Usually a grade of more than 16/20 is considered excellent. The following table is most commonly used by world institutions and universities to convert from the Iranian grading system:
References
Academic grading in Iran Wikipedia(Text) CC BY-SA