What Grade Do I Need on My Final? The Formula and Worked Examples
What grade do I need on my final? Use one formula, see worked examples and learn what to do when the answer tops 100%, with a free grade calculator.
By TheTextKit TeamPublished
Three inputs, a current grade of 88%, a final worth 30% and a 90% target, give a required final exam score of 94.7%.
What grade do I need on my final? Take your target course grade, subtract the part of it your current grade already covers, and divide what is left by the weight of the final. As a formula: needed = (target - current × (1 - weight)) ÷ weight. With an 88% grade, a final worth 30% and a 90% target, you need about 94.7% on the exam.
The answer tells you something at once: over 100 means the target is out of reach, and below 0 means you already have it. Here is the formula step by step, how to find your current grade, the three answers you can get and a quick way to check your own numbers.
What grade do I need on my final? The formula
You need three numbers, and your syllabus and gradebook have all of them:
- Current: your grade on everything except the final, as a percentage.
- Weight: how much the final counts, as a decimal. A final worth 25% is 0.25.
- Target: the course grade you want, as a percentage.
The formula comes straight from how gradebooks work. A course grade is the sum of each part's score times its weight. Sakai's help page gives a typical case: exams worth 20% averaging 90, assignments worth 40% averaging 75 and quizzes worth 40% averaging 85. They add up to 18 + 30 + 34 = 82 (how a percentage gradebook is calculated). The final is one more part, so your course grade equals current × (1 - weight) + final × weight. Set that equal to your target and solve for the final:
needed = (target - current × (1 - weight)) ÷ weight
A worked example, step by step
Say your grade before the final is 88%, the final counts for 30% and you want a 90%.
- Turn the weight into a decimal. 30% is 0.30, so the rest of the course is 0.70.
- Multiply your current grade by the rest. 88 × 0.70 = 61.6. That is what your finished work already adds to the course grade.
- Subtract that from your target. 90 minus 61.6 is 28.4. The final has to supply that much.
- Divide by the weight. 28.4 ÷ 0.30 = 94.67.
You need about 94.7%. Check it by running the formula forward: 61.6 + 0.30 × 94.67 = 90.0.
The formula (target minus current times one minus weight) divided by weight, with each variable labeled, and the worked example (90 minus 88 times 0.7) divided by 0.3 giving 94.7.
Find your current grade first
This is the step people get wrong. Your current grade is your average on everything except the final. It isn't your last exam score, and it may not be the number in your student portal: some gradebooks count unsubmitted work as zero and others skip it, so check which one yours does.
If your syllabus lists weighted categories, add up each category's score times its weight, then divide by the total weight you have graded so far, not by 100. Here is an example with a final worth 25%:
| Category | Weight | Your score | Points toward the course |
|---|---|---|---|
| Homework | 20% | 95 | 19.0 |
| Quizzes | 15% | 88 | 13.2 |
| Midterm | 25% | 82 | 20.5 |
| Projects | 15% | 92 | 13.8 |
| Total graded | 75% | 66.5 |
Your current grade is 66.5 ÷ 0.75 = 88.67%. Because 66.5 points are already banked, you can skip step 2 of the worked example. For a 90, you need (90 - 66.5) ÷ 0.25 = 94.0 on the final. For an 87, you need 82. For an 80, you need 54.
Homework 20% at 95, quizzes 15% at 88, midterm 25% at 82 and projects 15% at 92 add up to 66.5 points of 75, a current grade of 88.67%. The 25% final then needs 94.0% for a 90.
The Grade Calculator does this on its Weighted Course Grade tab, including the divide-by-graded-weight step.
What grade do I need on my final to get an A, B or C?
Run the formula once per target and you get a full menu of answers. First, though, know what the number means.
The three answers you can get
The number the formula gives falls into one of three zones.
| Result | Example | What it means |
|---|---|---|
| Over 100 | Current 84, final 25%, target 90: (90 - 63) ÷ 0.25 = 108 | Out of reach on the exam alone. You would need extra credit or a curve |
| 0 to 100 | Current 93, final 20%, target 90: (90 - 74.4) ÷ 0.2 = 78 | Reachable. The number is your goal |
| Below 0 | Current 95, final 20%, target 75: (75 - 76) ÷ 0.2 = -5 | You already have it. Even a 0 leaves you at 76 |
The Grade Calculator's "What Do I Need On My Final?" tab shows the same three zones as messages: it flags "Extra credit required" above 100 and "Guaranteed" at or below 0. Its weight field takes any value above 0 and below 100.
A menu of targets
Here is the earlier example, an 88% grade and a final worth 30%, run against round cutoffs. Your syllabus may use different ones.
| Target | Needed on the final |
|---|---|
| 90 | 94.7 |
| 87 | 84.7 |
| 80 | 61.3 |
| 70 | 28 |
| 60 | Nothing: you already have it |
Notice how steeply the numbers fall. Every point you take off the target saves you 1 ÷ weight points on the final, which is 3.3 points here. Moving from a 90 to an 87 cuts the requirement by 10 points. That is why a backup target is worth computing before the exam, not after.
How much does the final's weight matter?
A lot, and in a direction that surprises people. Keep the same 88% grade and 90% target and change only the weight:
| Final's weight | Score needed |
|---|---|
| 10% | 108 |
| 20% | 98 |
| 30% | 94.7 |
| 40% | 93 |
| 50% | 92 |
When you are below your target, a heavier final is good news, because it has more power to pull your average up. When you are above your target, the opposite holds: a heavier final means less cushion. With a 93% grade and a 90% target, a final worth 20% needs only a 78, but a final worth 50% needs an 87.
With a current grade of 88% and a target of 90%, a final worth 10% needs 108, 20% needs 98, 30% needs 94.7, 40% needs 93 and 50% needs 92. Anything over 100 is out of reach.
What if I bomb it? Find your floor
Planning only for the best case is how people get surprised. Run the formula forward instead. With an 88% grade and a final worth 30%, the course grade is 61.6 plus 0.30 times your final score:
| Final score | Course grade |
|---|---|
| 0 | 61.6 |
| 50 | 76.6 |
| 70 | 82.6 |
| 90 | 88.6 |
| 100 | 91.6 |
Look at the last row. Even a perfect final lifts this student only to 91.6. And the first row is your floor: compare it with the passing cutoff in your syllabus to see how much risk you carry.
With a current grade of 88% and a final worth 30%, a 0 on the final gives a course grade of 61.6, a 50 gives 76.6, a 70 gives 82.6, a 90 gives 88.6 and a 100 gives 91.6.
To see what the course grade does to your GPA, put it into the GPA Calculator.
Points, cutoffs and rounding in your syllabus
If your syllabus uses points instead of percentages
Some courses add up points and skip the weights. Then the math is subtraction. Subtract the points you have from the points you need for your target, and compare the result with the points the final is worth.
Say a course has 1,000 points in total, the final is worth 200 and you have 690 of the other 800. An A at 900 points needs 210 points from the final, which is more than the 200 available, so it is out of reach. A B- at 800 points needs 110 of 200, which is 55%. To convert points to a percentage, use the Percentage Calculator. Both methods give the same answer, since 690 of 800 is 86.25% and the percent formula gives 105 for the A and 55 for the B-.
Check the cutoff and rounding
The target in the formula is a number, and your instructor decides what it is. LSU's registrar says there is no university table of numerical equivalents for letter grades: the instructor must define the scale and put it in the syllabus (LSU plus/minus grade FAQ). The University of Memphis says the same (Memphis grading scale rules). So an A might start at 93 in one course and 90 in another.
Ask one more thing: does 89.5 round up to 90? If nobody has told you, aim for the exact cutoff and treat any rounding as a bonus. The Grade Calculator's final exam tab takes any target you type, so enter the cutoff from your syllabus. Its letter grades on the weighted tab use a common scale (93 for an A, 90 for an A-), which may not match yours.
Mistakes that throw the answer off
A few slips account for most wrong results.
- Using your last exam score as your current grade. Use the average of everything except the final.
- Typing the weight as 30 instead of 0.30. The formula needs the decimal, and the answer comes out wildly wrong if you forget.
- Mixing points and percentages. Pick one and keep it for every number.
- Ignoring dropped scores. If your instructor drops the lowest quiz, work out your current grade without it.
- Trusting a result of 97 or 98. It is technically reachable, but it asks for a near-perfect exam, so compute the next cutoff down as a backup.
Frequently asked questions
How do I calculate what I need on my final?
Use needed = (target - current × (1 - weight)) ÷ weight, with the weight as a decimal. For a current grade of 88%, a final worth 30% and a target of 90%, that is (90 - 88 × 0.7) ÷ 0.3 = 94.67. Current means your grade on everything except the final.
What if the grade I need is over 100%?
Then the target is out of reach on the final alone. Your options are extra credit if your instructor offers it, a curve if one is announced, or a lower target. Work out what you need for the next grade down, because that cutoff may be reachable.
What if other assignments are still due besides the final?
Estimate a realistic score for each, fold those scores into your current grade using their weights, and then run the formula for the final. The final's weight stays the same. Redo the math when the real scores arrive.
Can I still pass if I do badly on the final?
Run the formula forward: course grade = current × (1 - weight) + final × weight. With a current grade of 88% and a final worth 30%, even a 0 on the final leaves you at 61.6. Compare that with the passing cutoff in your syllabus.
Is it safe to enter my grades into an online calculator?
With TheTextKit's Grade Calculator, yes: it runs in your browser and nothing you type is sent to a server. Check that for any other tool before you enter anything you would not want shared.
Run your own numbers
So, what grade do I need on my final? Open your syllabus and write down the final's weight and the cutoff for the grade you want. Work out your current grade without the final, then open the Grade Calculator and use the "What Do I Need On My Final?" tab. If the answer is above 100, check the next grade down and talk to your instructor early, while there is still work left to do.
