How to Calculate a Weighted Average of Grades

Calculate a weighted average of grades by multiplying each grade value by its percentage weight, adding the weighted grade values, then dividing by the total weights. A syllabus that states 20% homework, 30% midterm, and 50% final exam already gives you every weight you need.

The four steps

1. List each assignment with its grade value and grade weight.
2. Multiply each grade value by its weight.
3. Add the weighted grade values into a weighted sum.
4. Divide the weighted sum by the total weights.

The simple average of 92, 78, and 85 reaches 85.00. The weighted average lands at 84.30 because the midterm, the weakest score after homework, carries 30% of the grade.

Grades that use points instead of percentages

Points work the same way. An assignment worth 150 points and a final worth 350 points give weights of 150 and 350. The division by the total of weights, 500, rescales everything, so converting points to percentages first changes nothing.

Final grade planning

Reverse the calculation to find the score you still need. With coursework of 72 already earned at a 40% weight, and a target course grade of 80:

An 85.33 on the final exam, worth 60%, finishes the course at exactly 80. Enter the same numbers in the weighted average calculator and adjust the final exam row until the result meets your target.

Common mistakes

• Averaging the percentages instead of the scores. Weights describe importance; they are not values to be averaged.
• Mixing units. Keep credits with credits and percentages with percentages inside one calculation.
• Dropping ungraded work. An assignment with no score yet is not a zero — leave the row out until the score exists.