A weighted grade calculator takes the percentage score you got on each assignment and how much that assignment is worth (its weight), then combines them into one overall grade using the weighted-average formula. Unlike a plain average, which treats a 5-point pop quiz the same as a 100-point final exam, a weighted grade reflects how much each piece of work actually counts toward your final mark. The free Grade Calculator does exactly that: you enter each assignment or exam with its score and weight, and it returns your weighted percentage and matching letter grade instantly as you type. Nothing is uploaded, every calculation runs locally in your browser, and weights are normalized automatically so the total does not need to equal 100. That makes it equally useful for a quick sanity check, a partway-through-term standing update, or a full what-if plan for an upcoming final exam.
What "Weighted" Actually Means (and Why It Matters)
Every graded item in a course carries a weight, which is simply how much that item is worth toward the final mark. A final exam worth 40% should pull your grade four times as hard as a homework assignment worth 10%, but a plain (unweighted) average would count them equally.
Consider two students who each earn a 90 and an 80 across their only two items. Under a plain average they both finish at 85, a B. Under a weighted calculation the split matters: a 90 on a midterm worth 50% and an 80 on a final worth 50% give (90 × 50 + 80 × 50) ÷ 100 = 85, a B, while an 80 on a midterm worth 30% and a 90 on a final worth 70% give (80 × 30 + 90 × 70) ÷ 100 = 87, also a B.
Now flip the weights on that same pair of scores: a 90 on work worth 70% and an 80 on work worth 30% give (90 × 70 + 80 × 30) ÷ 100 = 87, while an 80 on the 70% item and a 90 on the 30% item give (80 × 70 + 90 × 30) ÷ 100 = 83. The same two scores produce a 4-point gap depending on which carries the bigger weight, which is exactly the signal a weighted grade is designed to surface and the one a plain average would hide.
The Weighted Average Formula
The formula is short and worth memorizing:
grade = sum(score × weight) ÷ sum(weight)
Multiply each score by its weight, add all those products together, then divide by the sum of the weights. The result is a percentage between 0 and, in theory, higher than 100 if extra-credit work pushes it up.
For example, a 90 on an essay worth 50% and an 80 on a presentation worth 50% give (90 × 50 + 80 × 50) ÷ 100 = 85. Swap the essay score to 95 and you get (95 × 50 + 80 × 50) ÷ 100 = 87.5. The math is the same regardless of how many items you have; you just extend the list of products.
This is the formula the Grade Calculator runs in the background. You do not need to do it by hand; you just type the numbers and the answer appears below.
How to Use the Grade Calculator
The Grade Calculator is built around three fields per row: an optional name to keep track of what the row represents, the score you received as a percentage, and the weight of that item as a percentage of the final grade. Here is the workflow.
- Add a row for each assignment, quiz, lab, project, or exam you want to include.
- Type the score into the score field. If your instructor graded the work as 88 out of 100, enter 88.
- Type the weight into the weight field. For an item worth 20% of the final grade, enter 20.
- Use the Add row button for more items, or the remove button to delete a row you no longer need.
- Read your weighted grade and letter grade in the results panel below the table. The numbers update as you type, with no button to press.
- Spot-check the total weight the calculator reports. If your syllabus says the course adds to 100% and the tool shows 75, you have missed one of the categories.
Because the calculator runs locally in your browser, nothing is sent to a server. You can experiment freely, delete rows, or change scores without worrying about saving state or losing your work.
When Weights Don't Add Up to 100
A common surprise is that your weights do not need to total exactly 100 for the math to work. The formula divides by the actual sum of the weights, so the result is always a correct weighted average, regardless of how the inputs add up.
For example, weights of 20, 20, and 10 sum to 50. If the matching scores are 90, 85, and 80, the calculation is (90 × 20 + 85 × 20 + 80 × 10) ÷ 50 = (1800 + 1700 + 800) ÷ 50 = 4300 ÷ 50 = 86. That is the right answer even though the weights total only half of 100.
This auto-normalization is helpful in two situations. First, partway through a term you may not have every assignment graded yet; entering only the items that are in keeps your standing realistic instead of pretending the rest are zeros. Second, some instructors leave one category unweighted on purpose, so the math still works if you only enter the categories that have a stated weight. The calculator surfaces the total weight so you can spot missing items at a glance.
Planning Your Final Exam With What-If Scores
The most common reason students reach for a weighted grade calculator is final-exam planning. Once you have your existing graded items in the table with their correct weights, add the final as its own row and type only the final's weight into the weight field. Leave the score empty for now, or type a guess. The moment you type a number, the overall grade and letter grade below the table update.
Try a few values: type 70 and watch your overall grade climb into a B if the rest of the term is solid; type 80 and see whether a mid-range B or high B is realistic; type 90 and check whether an A is within reach. The score that pushes the overall percentage to the letter grade cutoff you want is the score you need on the final. Because the panel shows both the percentage and the letter grade at the same time, you do not have to flip between windows or do the arithmetic on paper.
This what-if workflow also works for any single remaining assignment, not just finals. If a big project is coming up, add it as a row with its weight and try different scores until you see the letter grade you want to lock in.
Letter Grade Cutoffs and Why Your Syllabus May Differ
The Grade Calculator uses the most common US letter-grade scale, which is shown below.
| Letter Grade | Percentage Range |
|---|---|
| A | 90 and above |
| B | 80 to 89 |
| C | 70 to 79 |
| D | 60 to 69 |
| F | Below 60 |
This convention is used by most US high schools and universities, but it is not universal. Some instructors set the A cutoff at 93 instead of 90, some award plus and minus grades at small thresholds on either side of the cutoff, and some schools pass at 50 rather than 60. Always confirm the scale on your course syllabus before you treat a particular number as a guaranteed letter grade.
Extra Credit, Score Limits, and Edge Cases
Scores above 100 are allowed and simply raise your weighted average. If your instructor offers bonus points, a 105 on a small assignment adds more than a perfect 100 would, and can offset a lower score elsewhere in the same category. The calculator does not cap inputs, so entering an extra-credit mark works the same way as any other score.
Weights, however, must be zero or positive numbers for the calculation to make sense. A negative weight has no real-world meaning in this context and would distort the formula, so sensible inputs are zero or positive values only.
Finally, scores below 60 pull the average down fast, especially when the weight is high. A 55 on a final worth 40% drops a 90 average elsewhere by 14 points (90 × 60 + 55 × 40 = 7600, ÷ 100 = 76). Tracking these high-weight, low-score items as they come in gives you an early read on whether you need a stronger finish elsewhere in the term.
Beyond This Calculator: GPA and Plain Averages
If you want to combine letter grades from several courses into a single GPA, the GPA calculation walkthrough covers the weighted 4.0 scale next. And if every item in a course counts equally with no weighting at all, an average calculator does the simpler arithmetic without weights.
For a deeper look, see Hexagon Area Formula: What It Is and How to Apply It.