How the weighted grade calculator works
Most syllabi split your grade into categories, something like homework 20%, quizzes 20%, exams 60%. Your overall grade is not the plain average of those three numbers. It is a weighted average, where each category counts in proportion to its weight. A 95 in homework is nice, but with exams worth three times as much, a 78 on exams will dominate the result.
Enter each category's grade and its weight from the syllabus. If your weights do not total 100 because the final project has not been graded yet, the calculator says so and computes the average over the weights you did enter, which is your true standing on the graded portion of the course.
The formula
Each category grade is your percentage in that category, each weight is its share of the course grade, and Σ means add up across every category you entered. When the weights total exactly 100, the denominator is simply 100.
Worked example
Your syllabus says Homework 20%, Quizzes 20%, Exams 60%, and your grades are 92%, 84% and 78%:
Grade = (92 × 20 + 84 × 20 + 78 × 60) ÷ 100 = (1,840 + 1,680 + 4,680) ÷ 100 = 82.00%, a B- on the plus / minus scale.
Your three grades average 84.67 on paper, but the real grade is 82.00. Weighting cost you 2.67 points, all of it because the category you are weakest in is the one carrying most of the course.
The three columns worth reading
The headline number tells you where you stand. The table underneath tells you what to do about it, and it is the part this calculator exists for.
Points it adds is what each category actually contributes to your grade. In the example above, homework contributes 18.40 points and exams contribute 46.80. Both those numbers are lower than the grades they came from, which confuses people until you notice they have to add up to 82.00 between them.
Room left in it is the interesting one. It is how much course grade is still sitting unclaimed in each category, which is the gap between your grade there and a perfect one, scaled by weight. Homework has 1.60 points left in it. Exams have 13.20. The category you are doing worst in is nearly always the one holding the most room, which is the exact opposite of where people instinctively spend their time. Bringing a 92 up to a 100 is hard and buys almost nothing. Bringing a 78 up to a 90 is easier and buys six times more.
10 more points is worth converts effort into grade. Ten points of improvement in a category worth 60% of the course moves your overall grade by 6.00 points. The same ten points in a category worth 20% moves it by 2.00. Same effort, a third of the result. This is the single most useful fact about weighted grading and almost nobody is ever shown it.
Why the plain average lies to you
Every result shows both numbers: your weighted grade, and the plain average of your category grades, along with the distance between them. That distance is not decoration. If your weighted grade sits well below your plain average, it is telling you something specific and fixable, which is that your effort and the course's priorities are pointing in different directions.
It is a very common shape. Homework is frequent, visible and gets done. Exams are rare, stressful and easy to put off. So students often end up with their best grades in the lightest category and their worst in the heaviest, and then find the final number lower than anything they recognise. There is nothing wrong with the student in that picture. There is a mismatch between where the work went and where the weight is, and it is a mismatch you can see in one table and fix in one week.
The mid-semester trick: partial weights
You do not have to wait until everything is graded. If only homework (20%) and quizzes (20%) have grades so far, say 90 and 80, enter just those two rows. The calculator computes (90 × 20 + 80 × 20) ÷ 40 = 85.00%, which is your standing on the graded 40% of the course. That is more honest than pretending the ungraded 60% is a zero or a hundred, and it is more useful too: it tells you the remaining 60% will count one and a half times as much as everything you have done so far, so the course is still very much winnable.
Which grading scale is yours?
Scales differ between schools, so this calculator asks rather than assuming. Most colleges use a plus / minus scale where an A starts at 93. Most US high schools use a straight 10-point scale where an A starts at 90. Some schools use the traditional 7-point scale, where an A also starts at 93 but the passing line is 70 rather than 60. A 91% is an A- on the first, a plain A on the second, and a B on the third, so if you are near a boundary the scale is not a detail.
Why your school portal may show something different
Usually a class policy rather than a maths error. The common causes are a dropped lowest quiz, assignments entered but not yet graded, extra credit sitting in a category you did not enter, and rounding applied only to the final course grade. If your portal disagrees, work down that list before assuming either number is wrong.