To calculate your final grade, multiply your current grade by the share of the class that is not the final exam, multiply your final exam score by the weight of the final, and add the two numbers. To find out what you need on the final, turn that around: needed score = (target grade − current grade × (100% − final weight)) ÷ final weight.
I built the final grade calculator on this site around that one formula, and I checked every example below by hand and again in code. Here is how it works, where people get it wrong, and how to set it up in a spreadsheet.
The final grade formula
Most classes treat your grade as two parts: everything before the final, and the final itself. Each part has a weight, and the weights add up to 100%.
Final grade = Current grade × (100% − Final weight) + Final exam score × Final weight
Say you have 84% going into the final, the final is worth 25%, and you score 92% on it.
- Everything before the final counts for 100% − 25% = 75%.
- Points from the work so far: 84 × 0.75 = 63.
- Points from the final: 92 × 0.25 = 23.
- Final grade: 63 + 23 = 86%.
What do I need on my final?
Before the exam, you know your current grade and the weight, and you want to know the score. Rearrange the formula:
Needed final score = (Target grade − Current grade × (100% − Final weight)) ÷ Final weight
Here are three cases I see all the time.
What do I need on my final to get an A?
You have 91% in the class. An A starts at 90% at your school. The final is worth 20%.
- Points already earned: 91 × 0.80 = 72.8.
- Points still needed: 90 − 72.8 = 17.2.
- Score needed on the final: 17.2 ÷ 0.20 = 86%.
So an 86% on the final keeps your A.
When the answer is more than 100%
You have 84% in the class and want to finish with 90%. The final is worth 25%.
- Points already earned: 84 × 0.75 = 63.
- Points still needed: 90 − 63 = 27.
- Score needed on the final: 27 ÷ 0.25 = 108%.
108% is above a perfect score, so a 90% is out of reach without extra credit. The best you can do with a perfect final is 63 + 25 = 88%. Aim for 85% instead and the score you need drops to (85 − 63) ÷ 0.25 = 88%.
What do I need on my final to pass?
You have 75% in the class. Passing is 60%. The final is worth 25%.
- Points already earned: 75 × 0.75 = 56.25.
- Points still needed: 60 − 56.25 = 3.75.
- Score needed on the final: 3.75 ÷ 0.25 = 15%.
So yes, in this case you can fail the final and still pass the class. You only need 15% on the exam. It gets tighter when your current grade is close to the line. With 62% in the class and a final worth 30%, you need (60 − 62 × 0.70) ÷ 0.30 = 55.3%. That is still a failing exam score at most schools, but there isn’t much room left.
One warning: some classes say you must pass the final to pass the class, whatever your average is. The formula can’t know that. Read the syllabus.
Final exam score needed: a quick table
This table shows the score you need on the final to finish the class with 80%. Find your current grade on the left and the weight of your final across the top.
| Current grade | Final worth 10% | Final worth 20% | Final worth 25% | Final worth 30% |
|---|---|---|---|---|
| 70% | 170% | 120% | 110% | 103.3% |
| 75% | 125% | 100% | 95% | 91.7% |
| 80% | 80% | 80% | 80% | 80% |
| 85% | 35% | 60% | 65% | 68.3% |
| 90% | Any score | 40% | 50% | 56.7% |
A heavier final cuts both ways. It gives you more room to climb when you’re behind, and more room to fall when you’re ahead.
How are final grades calculated when everything is weighted?
The formula above assumes you already know your current grade. If your portal doesn’t show one, you have to build it from the categories in your syllabus. That’s a weighted average: multiply each grade by its weight, add the results, then divide by the total weight you’ve entered.
| Category | Grade | Weight | Grade × Weight |
|---|---|---|---|
| Homework | 92% | 20% | 1,840 |
| Quizzes | 85% | 20% | 1,700 |
| Midterm | 78% | 25% | 1,950 |
| Total so far | 65% | 5,490 |
Grade so far: 5,490 ÷ 65 = 84.46%. The final exam is the missing 35%. To finish with 85%, you need (85 × 100 − 5,490) ÷ 35 = 86% on it.
Notice that the plain average of 92, 85 and 78 is 85%, not 84.46%. The weighted grade is lower because the midterm is the weakest grade and carries the most weight. Averaging your grades without the weights is the most common mistake I see. The weighted grade calculator does this sum for any number of categories and shows what you need on whatever is left.
If your class runs on points instead of weights, it’s simpler. Add up the points you earned, divide by the points possible and multiply by 100. With 190 points out of 220, your grade is 86.36%. The grade calculator for points and test scores handles that, and turns the result into a letter.
How to calculate a final grade from two semesters or quarters
A full-year grade from two semesters is usually a plain average, because each semester counts for half. With 84% in the first semester and 90% in the second, the year grade is (84 + 90) ÷ 2 = 87%.
A semester grade built from two quarters and an exam is a weighted average again. A common setup is 40% for each quarter and 20% for the exam. With 86% and 91% in the quarters and 84% on the exam:
- Quarter 1: 86 × 0.40 = 34.4.
- Quarter 2: 91 × 0.40 = 36.4.
- Exam: 84 × 0.20 = 16.8.
- Semester grade: 34.4 + 36.4 + 16.8 = 87.6%.
Want an A for that semester? You’d need (90 × 100 − 86 × 40 − 91 × 40) ÷ 20 = 96% on the exam. Schools set these weights differently, so check your handbook, then put your own numbers into the semester grade calculator.
How to calculate final grade in Excel or Google Sheets
These formulas work the same in Excel and Google Sheets. Put your current grade in B1, your target in B2 and the weight of the final in B3. Type them as percentages, such as 84%, 90% and 25%. The score you need is:
=(B2-B1*(1-B3))/B3Format the cell as a percentage. With those three numbers it shows 108%. To get your final grade after the exam, put your exam score in B4:
=B1*(1-B3)+B4*B3For weighted categories, list the grades in B2 to B4 and their weights in C2 to C4. SUMPRODUCT multiplies each pair and adds the results, which is exactly the weighted average sum:
=SUMPRODUCT(B2:B4,C2:C4)/SUM(C2:C4)With the homework, quiz and midterm numbers above, that returns 84.46. Dividing by the sum of the weights matters. It keeps the answer right when the weights you’ve entered don’t add up to 100% yet.
Mistakes that change the answer
- Using the wrong current grade. If work is still ungraded or missing, the number in your portal will move.
- Guessing the weight. Get the real figure from the syllabus. If the class uses points, divide the final’s points by the total points in the class.
- Forgetting dropped or replaced scores. Some teachers drop your lowest quiz or let the final replace your lowest test. Recalculate your current grade first.
- Counting on rounding. Many schools round 89.5% up to 90%. Many don’t.
- Using the wrong letter scale. I use the common scale here: A is 90%, B is 80%, C is 70% and D is 60%. Some schools set an A at 93%.
Questions people ask about final grades
How do I calculate what I need on my final exam?
Multiply your current grade by the share of the class that is not the final. Subtract that from the grade you want. Divide the result by the weight of the final. With 84% now, a target of 85% and a final worth 25%, you need (85 − 84 × 0.75) ÷ 0.25 = 88%.
How much do I need on my final to pass?
Use the same formula with your school’s passing grade as the target. With 75% in the class, a passing grade of 60% and a final worth 25%, you need 15%. If the answer comes out at zero or below, you have already passed on your average, unless your class requires a minimum score on the exam itself.
How do I calculate my final grade after the final exam?
Multiply your grade before the exam by the share of the class it covers, multiply your exam score by the weight of the final, and add them. With 84% before the exam, a final worth 25% and a 92% on it, your final grade is 63 + 23 = 86%.
How do I calculate a final grade with different weights?
Multiply each category grade by its weight, add the results and divide by the total weight. With 90% on work worth 40% and 80% on work worth 60%, the grade is (90 × 40 + 80 × 60) ÷ 100 = 84%.
How do I calculate a final grade from two semesters?
If each semester counts for half, add the two grades and divide by 2. With 84% and 90%, the year grade is 87%. If your school adds a separate final exam, treat it as a weighted average instead.
If you’d rather skip the arithmetic, the final grade calculator gives you the answer as you type and shows the best grade you can still reach. And if you need a calculator like these on your own WordPress site, start a discussion with Swift Web Dev. Building them is what I do.
