What a weight means
A weight tells you how much a category contributes to the course grade. If exams are worth 50% and homework is worth 20%, a five-point change in the exam average affects the overall grade more than the same five-point change in homework.
The weighted-average formula
Multiply each category grade by its weight, add the weighted results, then divide by the total weight used. If weights add to 100%, the formula can be written as Σ(grade × weight) ÷ 100 when weights are entered as percentages.
Worked example
Suppose exams are 88% at 40%, assignments are 92% at 35%, and quizzes are 80% at 25%. The contributions are 35.2, 32.2 and 20. Add them to get an estimated weighted grade of 87.4%.
When weights do not total 100%
A gradebook may show only categories graded so far. If visible weights total 70%, normalizing them can estimate performance on completed work, but it is not the same as the final course grade because future categories still have influence.
Rules that change the official result
Dropped scores, extra credit, category caps, minimum exam requirements and rounding policies can all change the grade. Use the syllabus or official gradebook as the final authority and treat the calculator as a planning model.
Why category changes can feel surprising
A small category with a perfect score may barely move the course average, while one large exam can shift it several points. That is not a calculator error; it is the purpose of weighting. Before worrying about an individual score, check how much of the final grade that score or category actually controls.
Related resources
Reviewed: October 2026. CurioLift explanations are educational; when a school, instructor or required style guide uses different rules, those rules take priority.