Short answer: weighted grade = sum of (score × weight), with weights as decimals that add up to 1. If the weights do not total 100%, divide by the total weight.
What a Weighted Grade Is
A weighted grade combines several scores into one number, and each score counts in proportion to its weight. A final exam worth 40% moves your result four times as much as a set of quizzes worth 10%. This guide is the how-to. If you want to understand why courses are graded this way, read our explainer on what a weighted grade is and how it works.
The Formula
Write each weight as a decimal, so 20% becomes 0.20. When the weights add up to 100% (a total of 1), the sum is already your grade. If they do not, divide by the total weight, as shown later in this guide.
Step-by-Step Example
A course has four components. Your scores are shown as percentages.
| Component | Weight | Your score | Weighted points |
|---|---|---|---|
| Assignments | 20% | 88% | 17.6 |
| Quizzes | 10% | 76% | 7.6 |
| Midterm | 30% | 68% | 20.4 |
| Final exam | 40% | 72% | 28.8 |
| Weighted grade | 100% | 74.4 |
- Convert each weight to a decimal: 0.20, 0.10, 0.30 and 0.40.
- Multiply each score by its weight: 88 × 0.20 = 17.6, and so on down the table.
- Add the results: 17.6 + 7.6 + 20.4 + 28.8 = 74.4%.
Why Not Just Average the Scores?
A simple average of the four scores is (88 + 76 + 68 + 72) ÷ 4 = 76.0%. That is 1.6 points higher than the correct weighted grade, because the two heaviest components, the midterm and the final, were your lowest scores. A simple average treats every component as equal, so it overstates your grade when your strongest work is in the lightest components, and understates it when the reverse is true.
When a Category Has Several Items
Most weights are given to categories, and a category often contains several items. First turn the category into one percentage, then apply its weight. Suppose three assignments scored 18 out of 20, 40 out of 50 and 27 out of 30.
- Pooled marks: (18 + 40 + 27) ÷ (20 + 50 + 30) = 85 ÷ 100 = 85%.
- Average of percentages: (90 + 80 + 90) ÷ 3 = 86.67%.
The two methods differ because the assignments have different totals. Use whichever your syllabus describes. Pooling is common when items are marked out of different totals, and averaging is common when each item is meant to count equally.
When the Weights Do Not Add Up to 100%
Sometimes the weights you have add up to less than 100%, for example when one component has not been graded yet, or when a syllabus gives a partial list. Suppose the graded components are worth 15%, 25%, 30% and 20%, a total of 90%, and your scores are 80, 70, 60 and 90. The weighted points are 12 + 17.5 + 18 + 18 = 65.5. Divide by the total weight of 0.90 to put the result back on a 0 to 100 scale: 65.5 ÷ 0.90 = 72.78%. That is your grade on the work graded so far. For how this connects to a final exam, see our guide on calculating your current grade.
When Weights Are Given as Points
Some courses state weights as points instead of percentages. In that case the weight of each component is simply its share of the total points. Suppose assignments are worth 150 points, tests 200 and a project 50, a total of 400. You earned 120, 160 and 45. Then (120 + 160 + 45) ÷ 400 = 325 ÷ 400 = 81.25%. Points-based grading is a weighted grade where each component’s weight is the points it carries, so no separate weighting step is needed.
Turning the Percentage Into a Letter Grade
Calculate the percentage first, then convert it using your institution’s grading scale. Do not convert each component to a letter before weighting, because letters throw away detail. A 74.4% is a different letter at different institutions, and some round up at a boundary while others do not. Use the table that applies to you, and check whether it uses whole numbers or decimals.
Checking Your Work
Three quick checks catch most errors. First, your weighted grade must sit between your lowest and highest component scores, which is 68 to 88 in the example. Second, the weights you used should add up to the total you expect. Third, compare the result with the simple average. If the heaviest components are your weakest, the weighted grade should be lower, and if they are your strongest, it should be higher. When a result fails one of these checks, look for a weight entered as a whole number instead of a decimal.
Tracking Your Weighted Grade Through the Term
Recalculate after each returned assessment. Using the example course, suppose the final has not been taken yet. Your graded work is worth 20 + 10 + 30 = 60% and earned 17.6 + 7.6 + 20.4 = 45.6 weighted points. Divide by the weight completed: 45.6 ÷ 0.60 = 76.0% on the work so far. When the final arrives and you score 72%, the full weighted grade becomes 74.4%, so the exam pulled your overall result down by 1.6 points. Seeing the trend as it develops gives you time to respond.
Calculating a Weighted Grade in a Spreadsheet
A spreadsheet saves effort when you track several courses. Put the component names in column A, the weights in column B and your scores in column C. If the weights are decimals that add up to 1, the formula =SUMPRODUCT(B2:B5,C2:C5) gives the weighted grade. If the weights are percentages or do not total 100%, use =SUMPRODUCT(B2:B5,C2:C5)/SUM(B2:B5) so the result stays on the same scale as your scores. Keep the unmarked components blank and your tracker updates as scores arrive.
Common Mistakes to Avoid
- Averaging the scores without weights. Always multiply by the weights first.
- Using 20 instead of 0.20. Convert percentages to decimals, or divide by 100 at the end.
- Forgetting to divide by the total weight. This matters when weights do not add to 100%.
- Averaging item percentages in a category with different totals. Check whether marks are pooled.
- Rounding too early. Round only the final answer.
- Converting to letters before weighting. Weight the percentages, then convert.
Check Your Work With BioScribe
BioScribe’s Grade Calculator calculates weighted grades and finds the score you need on your final exam. Enter the four components from the example above and check that you reach 74.4%, then try your own course.
Frequently Asked Questions
Do I have to convert weights to decimals?
Not strictly. You can multiply by the percentage and divide the total by 100. Converting 20% to 0.20 is simply easier to enter into a calculator.
What if my weights add up to more than 100%?
Check the syllabus for an error or for extra credit. If the total is correct, dividing by the total weight keeps the result on a 0 to 100 scale, but confirm with your instructor first.
Does the order of the components matter?
No. Multiplication and addition give the same answer in any order, so list the components however you like.
How do I include extra credit?
Follow your syllabus. Extra credit is usually added to the points earned in a category, sometimes with a cap, before the category percentage is calculated.
Can I do this in a spreadsheet?
Yes. Put scores in one column and weights in another, then use the SUMPRODUCT function to multiply and add them in one step.
Conclusion
A weighted grade is the sum of each score times its weight. Convert categories to percentages first, divide by the total weight when it is not 100%, and run the three checks above. Once you have the method, you can answer questions like how a poor quiz will affect your grade, or what you need on the final exam, in a minute or two.
