How to Calculate a Weighted Grade

A weighted grade multiplies each category's percentage score by how much that category counts toward your final grade, then adds the results together. Homework, quizzes, exams, and projects each carry a different share of the total, and the formula reflects that instead of treating every assignment equally.

This is for anyone with a course syllabus that lists grading categories by percentage (like "Homework 20%, Midterm 30%, Final Project 50%") and wants to check their current standing before an assignment is graded and posted.

The formula

Weighted grade = Σ (category score × category weight)

Σ just means "sum of": calculate each category's contribution separately, then add them all up. The category weights should be expressed as decimals for the multiplication (20% becomes 0.20), and the results are then added, not averaged again.

Worked example

A course with three categories: Homework at 92%, worth 20% of the grade. Midterm at 85%, worth 30%. Final project at 88%, worth 50%.

(92 × 0.20) + (85 × 0.30) + (88 × 0.50) = 18.4 + 25.5 + 44.0 = 87.9%.

Reading a syllabus's grading breakdown correctly

Most syllabi list grading categories as a simple percentage table, but a few details are easy to misread. Some courses have sub-weighted categories, for example "Homework 20% (10 assignments, equally weighted)," meaning you first average the ten homework scores, then apply the 20% weight to that average, rather than weighting each individual assignment separately. Others explicitly state a lowest-score drop policy, which changes which scores go into your category average. Read the full grading section, not just the top-level percentages, before running the calculation.

Why weights should add up to 100%

If your category weights don't sum to 100%, the weighted average will be misleading. If they only total 80%, your calculated grade will understate your actual grade proportionally, since 20% of the possible weight was never accounted for in the formula. Add up every listed category weight before calculating anything else; a syllabus typo or a category you've overlooked is a common source of a number that doesn't add up.

Score vs. percentage

If an assignment is graded out of points rather than a straight percentage, like 46 out of 50, convert it first: 46 ÷ 50 = 92%. Entering raw score and max score, rather than a rounded percentage, avoids small rounding errors compounding across several assignments in the same category, which matters more the more assignments feed into one category average.

Common mistakes

• Averaging category scores directly instead of weighting them, which treats a 50% final project the same as a 5% pop quiz.
• Forgetting a sub-weighted category, and applying the top-level weight to a single assignment instead of the category average.
• Leaving an ungraded assignment out of a category average instead of factoring in its zero, or vice versa, depending on your instructor's stated policy for missing work.
• Rounding each category's contribution before adding, rather than rounding only the final total, which can shift a borderline grade by a fraction of a point.

Run the full calculation, including a "what score do I need on my final" solver, with the grade calculator.