The short answer
Semester grade = Q1 × w₁ + Q2 × w₂ + exam × wₑ (weights as decimals that add to 1). With 88% and 84% in the quarters and an 80% exam on a 40/40/20 split: 88 × 0.4 + 84 × 0.4 + 80 × 0.2 = 84.8% (B). To finish with an 87% (B+) you’d need 91% on the exam; a 90% is out of reach (106%).Many high schools build a semester grade from three parts: two quarter (or nine-week) grades and a semester exam. The split varies by district and sometimes by course, which is why the same quarter grades can lead to different semester grades in different schools. Pick your weights and the calculator does the rest.
How the semester grade formula works
Semester grade = Q1 × w₁ + Q2 × w₂ + exam × wₑ, with the weights written as decimals that add up to 1.
Worked example on a 40/40/20 split: Q1 88%, Q2 84%, exam 80%.
- Q1: 88 × 0.40 = 35.2
- Q2: 84 × 0.40 = 33.6
- Exam: 80 × 0.20 = 16.0
Total: 84.8%, a B. If the weights you enter don’t add up to 100, the calculator divides by their total, so only their proportions matter — 2/2/1 gives the same answer as 40/40/20.
Common weight splits compared
The table below keeps the same quarters (88% and 84%) and changes only the split. Every number is computed with the formula above.
| Split (Q1 / Q2 / exam) | Exam 100% | Exam 80% | Exam 60% | Exam 0% | Exam needed for 87% |
|---|---|---|---|---|---|
| 40 / 40 / 20 | 88.8% | 84.8% | 80.8% | 68.8% | 91% |
| 45 / 45 / 10 | 87.4% | 85.4% | 83.4% | 77.4% | 96% |
| 37.5 / 37.5 / 25 | 89.5% | 84.5% | 79.5% | 64.5% | 90% |
Two things stand out. First, a small exam weight protects you: on 45/45/10, even a zero only drops you to 77.4%. Second, a small weight also limits you — reaching an 87% takes 96% on the exam, because the exam can’t move the grade far. A bigger exam weight cuts both ways.
Working backward: what do I need on the exam?
Switch the calculator to What I need on the exam and enter the semester grade you want. The formula flips:
needed = (goal − Q1 × w₁ − Q2 × w₂) ÷ wₑ
With 88% and 84% on a 40/40/20 split, an 87% (B+) needs (87 − 35.2 − 33.6) ÷ 0.2 = 91%. A 90% (A−) would need 106% — not possible without extra credit. The table under the result shows the exam score needed for every letter from A down to D−, marking the ones already secured and the ones out of reach.
What do I need on my semester exam to keep an A?
This is the most common semester test calculator question, and the answer depends on two things: how far above 90 your quarters are, and how much the exam weighs. The table assumes both quarters have the same grade, and uses needed = (goal − quarter average × quarter share) ÷ exam share.
Exam score needed to finish the semester at 90% (A−) or 93% (A)
| Quarter grades | 40/40/20, keep 90 | 40/40/20, reach 93 | 45/45/10, keep 90 | 37.5/37.5/25, keep 90 |
|---|---|---|---|---|
| 90 and 90 | 90% | 105% (not possible) | 90% | 90% |
| 92 and 92 | 82% | 97% | 72% | 84% |
| 94 and 94 | 74% | 89% | 54% | 78% |
| 96 and 96 | 66% | 81% | 36% | 72% |
Worked example for the second row: on 40/40/20, quarters of 92 bank 92 × 0.8 = 73.6 points. To finish at 90 you need 16.4 more from an exam worth 20, so 16.4 ÷ 0.2 = 82%.
Three patterns are worth knowing:
- Sitting right at 90 leaves no cushion. You must score 90 on the exam just to stay there, whatever the split.
- A small exam weight is a safety net. On 45/45/10, a student with two 94s keeps the A− with only a 54.
- Moving up is harder than staying. Reaching a solid A from two 90s would take more than 100% on a 40/40/20 exam.
If your quarters differ, enter both in the calculator above and switch to “What I need on the exam”. For a single class where the final sits on top of one running grade, the grade needed on final exam tool is quicker. To get a quarter grade from homework, quizzes and tests first, use the class grade calculator with categories, and turn one exam into a percent with the test grade percentage calculator.
Year-long courses and custom weights
Some courses run all year and end with one final exam. Tick Year-long course to add quarters 3 and 4. The presets keep the exam’s share and split the rest evenly — 40/40/20 becomes 20% for each quarter plus a 20% exam. With quarters of 88, 84, 86 and 85 and an 80 on the exam, that gives 84.6%.
Schools also mix it differently: some count semesters, not quarters, toward a year grade; some give the second quarter more weight than the first. Choose Custom and type each weight. Editing any weight switches the preset to Custom automatically, so you can start from a preset and adjust it.
Mistakes that throw the answer off
- Using the portal’s running grade as Q2 before the quarter ends. It may change. Run the calculator again when the quarter closes.
- Rounded quarter grades. If your report card shows 89 but the gradebook says 88.6, use the gradebook number when you have it.
- Exams inside a quarter. If your “final” is just a test inside Q2, it isn’t a separate exam weight — use the grade calculator instead.
- Semester vs. year exam. Make sure the exam covers the period you’re calculating.
Related tools
- One class with a single final percentage? The final grade calculator does it in one step.
- Need your quarter grade from categories first? Start with the grade calculator.
- After the semester, update your high school GPA or your cumulative GPA.
- Checking an exam score from points or wrong answers: the test score calculator.
Frequently asked questions
How do I calculate my semester grade?
What does 40/40/20 mean?
How are semester grades calculated in high school?
How do I average quarter 1 and quarter 2?
Does the semester exam count more than a quarter?
What do I need on my exam to get an A for the semester?
How does a year-long course work?
Can the exam lower my semester grade?
Sources & method
- Formula: weighted average of quarter grades and exam score, computed in your browser. Weight presets are common examples; check your own school’s handbook.
- Letter grades use the common US plus/minus scale (A 93, A− 90, B+ 87…). See the grading scale converter for others.
Formulas checked October 2026. Spotted an error? Tell us via the about page.