How weighted grading works
A weighted syllabus splits your grade into categories and fixes how much each one is allowed to matter before the semester starts. Homework 20%, quizzes 15%, midterm 25%, final 40%. Those percentages are an allocation, not a description of workload: fourteen homework assignments and one final exam can be worth 20% and 40% respectively, which means a single exam question is worth more to your grade than an entire homework set.
Each category is averaged on its own first. Then the category averages are blended in proportion to their weights. Doing it in that order is what makes weighting different from a plain average, and it is why adding one more perfect homework score to an already-strong category barely moves anything.
The formula
The denominator is the sum of the weights you actually entered — not a hard-coded 100. Mid-semester, that is the point. If only 60% of your grade has been graded, dividing by 60 gives you an accurate picture of the work that exists. Dividing by 100 would silently treat the ungraded 40% as zeros.
A worked example
These are the values loaded above. It is week ten and three of four categories have grades:
Quizzes — 81% at 15% weight
Midterm — 78% at 25% weight
numerator = (96 × 20) + (81 × 15) + (78 × 25)
numerator = 1,920 + 1,215 + 1,950 = 5,085
denominator = 20 + 15 + 25 = 60
grade = 5,085 ÷ 60 = 84.75%
84.75% on completed work — a B on a plus/minus scale. The other 40% is a blank the final exam will fill, so the honest range for the course is 50.85% (a zero on the final) to 90.85% (a perfect one). The calculator shows that range as a scenario table so you can see where each possible exam score actually lands you, and it flags the lowest score that still clears your target.
Which assignment is actually worth your evening?
The number that decides this is not the assignment’s point value — it is the weight of its category divided by how crowded that category is:
In the example above, acing one more homework assignment out of ten moves the course grade by roughly 0.08 points. One point on the final moves it by 0.40 — five times more, for one question. That asymmetry is the entire practical lesson of weighted grading, and it is worth checking before you spend Sunday on the wrong thing.
What breaks the formula
Dropped scores. “We drop your two lowest quizzes” means your quiz average should be computed without them. Do that by hand and enter the corrected average.
Empty categories. If a 10% participation category never gets an entry, that 10% goes somewhere — redistributed proportionally, or awarded as full credit at the end. These produce different grades. Ask which one applies.
Conditional weights. Some syllabi say the final replaces a lower midterm, or that the lowest exam counts half. Decide which branch applies to you first, then enter those weights.
Once you have your current grade, take it to the final grade calculator to see exactly what the exam needs to be. If your class is graded in raw points, the points-based calculator skips the conversion entirely. And there is a longer walkthrough in how weighted grades work.