Schools and universities across the United States and Canada determine their own GPA equivalents for letter grades, therefore there is no universal equivalent in GPA or percent marks for letter grades. While there are some tools online that may help you estimate your GPA based on letter grades, it is best to check with your own school or academic institution to determine the equivalents for your grades.
Most high schools and nearly all colleges and universities use the four-point grade point average system. Under this system, the GPA value for letter grades is equivalent to "4" for the grade "A", "3" for a "B", "2" for a "C", "1" for a "D" and "0" for "F." Additionally, most schools add or subtract a ".33" for a "+" or a "-" grade, so an "A+" would be equivalent to 4.33, and "B-" would be worth 2.67.
Some schools award higher grades for more difficult courses, in order to reflect the varying level of skill needed for different courses. This is intended to prevent students from selecting courses that are known to be easy sources of good grades. This practice is known as the weighted grade point average system, and it usually awards 4.5 or 5 points for an "A" letter grade.