The short answer
Most course grades are a weighted average. Each category (homework, quizzes, tests, final exam) has a weight from the syllabus, and your grade is the sum of each category score multiplied by its weight.
Course grade = Σ (category score × weight)
Example: a full course grade
| Category | Score | Weight | Contribution |
|---|---|---|---|
| Homework | 95% | 15% | 14.25 |
| Quizzes | 82% | 25% | 20.50 |
| Midterm | 76% | 30% | 22.80 |
| Final exam | 84% | 30% | 25.20 |
| Course grade | 100% | 82.75 |
82.75% displays as 82.8%, a B− on the common scale. Notice that a 95% homework average adds only 14.25 points because homework is just 15% of the grade.
What do I need on the final?
Before the final, you know everything except the exam score. Split the course into “work so far” (your current grade, worth 1 − final weight) and the final exam:
Target = current grade × (1 − w) + final score × w
Final score needed = (target − current grade × (1 − w)) ÷ w
Here w is the final’s weight as a decimal.
Example: your current grade is 82% and the final is worth 25%. For an 85% course grade: (85 − 82 × 0.75) ÷ 0.25 = (85 − 61.5) ÷ 0.25 = 94.0%. For an 80%: (80 − 61.5) ÷ 0.25 = 74.0%.
The final grade calculator does this instantly and shows the score needed for every letter grade.
Your grade before every category is graded
During the term, some categories (like the final) have no scores yet. Gradebooks then usually show your current grade: the weighted average of the categories graded so far, divided by the weights that have been used.
Current grade = Σ (category score × weight) ÷ Σ weights graded so far
Canvas, for example, leaves assignment groups with no graded work out of the calculation and rescales the weights of the rest. Using the example above without the final: (14.25 + 20.50 + 22.80) ÷ 70% = 57.55 ÷ 0.70 = 82.2%, a B−. Use that current grade in the final grade calculator to see what you need on the exam.
Points-based classes
Some classes don’t use weighted categories. Every assignment has a point value, and your grade is total points earned ÷ total points possible. In that system, big assignments automatically count more. For example, 450 earned out of 500 possible is 90%. Use the “Total points” mode in the grade calculator.
Things that change the math
- Dropped scores. If the lowest quiz is dropped, recalculate that category’s average without it.
- Final replaces a test. Some teachers replace your lowest test with your final score. Enter the categories as they’ll look after the replacement.
- Extra credit. It can push a category above 100%.
- Minimum exam rules. Some courses require a minimum exam score to pass regardless of your average. Check your syllabus.
- Curves. A curve changes scores after the fact. The formulas above use the scores you actually receive.
Frequently asked questions
How much will my final exam affect my grade?
At most, the final can move your grade by its weight. A final worth 20% can raise or lower your course grade by up to 20 points compared to scoring 0% or 100% on it. Use the table in the final grade calculator to see the effect for your numbers.
Can my final exam drop my grade by a whole letter?
Yes, if the final is heavily weighted and you score far below your current grade. With an 85% current grade and a 30% final, scoring 50% on the final gives 85 × 0.70 + 50 × 0.30 = 74.5%, a drop from a B to a C. With a 10% final, the same exam score only takes you to 81.5%, a B−.
Why does my gradebook show a different current grade?
Gradebooks often calculate using only graded categories, and some don’t count the final until it’s entered. Make sure you’re comparing like with like, and check whether any scores are missing or excused.
What if I need more than 100%?
The target isn’t reachable with the final alone. Ask about extra credit or retakes, and use the calculator to find the best grade you can still reach. If that’s a D, see is a D a passing grade? to check whether it still counts for credit and requirements.
Sources
- Instructure Canvas guide: How do I weight the final course grade based on assignment groups? (each group’s score × its weight, added together; groups without graded items are removed and the rest rescaled; checked 10 November 2026).
- Indiana University Knowledge Base: How categories and weighting affect grade calculation (weighted categories combined into the course grade; checked 10 November 2026).