Calculating a grade point average (GPA) involves combining the grades in several classes into a single numeric grade. This tutorial explains how to calculate an unweighted GPA and a weighted GPA.
First, one needs to map letter grades to a numeric scale. A 4.0 scale is the most common. But, each school has its own mapping from letter grades to numeric grades. This table shows a typical mapping.
Letter Grade |
Numeric Grade |
A |
4.0 |
B |
3.0 |
C |
2.0 |
D |
1.0 |
F |
0.0 |
Some schools allow positive (+) and negative (-) modifiers to letter grades, such as B+ and A-. These are usually translated into additions and subtractions from the numeric grade. One approach adds or subtracts 0.3 grade points. Thus, an A- is 4.0 – 0.3 = 3.7 and a B+ is 3.0 + 0.3 = 3.3. An A+ would be the equivalent of a 4.3. It seems a little strange to have a grade greater than 4.0 on a 4.0 scale, but that’s the way some schools assign numeric equivalents of letter grades.
Combining the grades in multiple classes involves calculating a weighted or unweighted average, depending on whether one is calculating a weighted of unweighted GPA.
The unweighted GPA is a simple average of the student’s grades, equal to the sum of the numeric grades divided by the number of classes.
Suppose a student has earned the following grades in their classes.
Class |
Letter Grade |
English |
A+ |
Social Studies |
A |
History |
A- |
Foreign Language |
B+ |
Math |
C+ |
Science |
B |
The first step in calculating an unweighted GPA is to translate the letter grades into numeric equivalents:
Class |
Letter Grade |
Numeric Grade |
English |
A+ |
4.3 |
Social Studies |
A |
4.0 |
History |
A- |
3.7 |
Foreign Language |
B+ |
3.3 |
Math |
C+ |
2.3 |
Science |
B |
3.0 |
Next, calculate the sum of the numeric grades:
4.3 |
4.0 |
3.7 |
3.3 |
2.3 |
+ 3.0 |
20.6 |
Then divide this sum by the number of classes, 6, yielding:
20.6 |
÷ 6 |
3.43 |
Thus, 3.43 is the student’s unweighted GPA on a 4.0 scale.
The purpose of the weighted GPA is to adjust for differences in class difficulty. There are several different approaches. One approach involves assigning a different number of credits to each class, corresponding to the class’s difficulty. Another approach involves incrementing the grade in each class according to the difficulty level.
To calculate the weighted GPA according to the first approach, multiply each grade by the number of credits earned in the class before summing the result, and divided the sum by the total number of credits.
For example, start with the grades and number of credits for each class.
Class |
Letter Grade |
Numeric Grade |
Credits |
English |
A+ |
4.3 |
4 |
Social Studies |
A |
4.0 |
4 |
History |
A- |
3.7 |
3 |
Foreign Language |
B+ |
3.3 |
3 |
Math |
C+ |
2.3 |
5 |
Science |
B |
3.0 |
5 |
Multiply each grade by the number of credits and sum the result.
Numeric Grade |
Credits |
Product |
4.3 |
4 |
17.2 |
4.0 |
4 |
16.0 |
3.7 |
3 |
11.1 |
3.3 |
3 |
9.9 |
2.3 |
5 |
11.5 |
3.0 |
5 |
15.0 |
Sum |
24 |
80.7 |
Divide the sum of products by the total number of credits:
80.7 |
÷ 24 |
3.36 |
Thus, 3.36 is the student’s weighted GPA on a 4.0 scale. Students often assume that a weighted GPA will be higher than an unweighted GPA. But, if the classes with lower grades are more challenging, they may drag down the weighted GPA.
Another approach involves adding 0.5 grade points to the grades in Honors classes and 1.0 grade points to the grades in AP or IB classes.
For example, start with the grades and difficulty level of each class.
Class |
Letter Grade |
Numeric Grade |
Level |
English |
A+ |
4.3 |
Honors |
Social Studies |
A |
4.0 |
Regular |
History |
A- |
3.7 |
Regular |
Foreign Language |
B+ |
3.3 |
Regular |
Math |
C+ |
2.3 |
Regular |
Science |
B |
3.0 |
AP |
Make the corresponding adjustment for each class’s grade.
Numeric Grade |
Level |
Grade Adjustment |
Adjusted Grade |
4.3 |
Honors |
0.5 |
4.8 |
4.0 |
Regular |
0.0 |
4.0 |
3.7 |
Regular |
0.0 |
3.7 |
3.3 |
Regular |
0.0 |
3.3 |
2.3 |
Regular |
0.0 |
2.3 |
3.0 |
AP |
1.0 |
4.0 |
Next, calculate the sum of the adjusted grades:
4.8 |
4.0 |
3.7 |
3.3 |
2.3 |
+ 4.0 |
22.1 |
Then divide this sum by the number of classes, 6, yielding:
22.1 |
÷ 6 |
3.68 |
Thus, 3.68 is the student’s unweighted GPA on a 4.0 scale.