Quick answer: Your grade is the weighted average of your scores: 85 (20%), 90 (15%) and 78 (25%) give 5,000 ÷ 60 = 83.33%, and with a 40% final you need 75% on it to finish at 80%.
How it's calculated
Weighted grade = Σ(score × weight) ÷ Σ weight. Only the work graded so far counts, so the result is your grade on what has been marked.
Score needed on the final = (target × (graded weight + final weight) − Σ(score × weight)) ÷ final weight. When all weights add up to 100%, this is the same as (target − points already earned) ÷ final weight.
Scores are percentages. If an item is marked out of another total (for example 18 out of 25), turn it into a percentage first: 18 ÷ 25 = 72%.
Worked examples
- 85 (20%), 90 (15%), 78 (25%): (1,700 + 1,350 + 1,950) ÷ 60 = 83.33%
- Final worth 40%, target 80%: (80 × 100 − 5,000) ÷ 40 = 75%
- Same work, target 90%: (90 × 100 − 5,000) ÷ 40 = 100%
Frequently asked questions
Do the weights need to add up to 100?
Not for the current grade: it is the average of what has been graded. For the final-exam answer, the graded weights plus the final weight should be 100% or less.
What if I need more than 100% on the final?
Then the target cannot be reached with the final alone. Check whether there is extra credit, or lower the target to see what is possible.
How do I enter a score like 18/25?
Convert it to a percentage first: 18 ÷ 25 × 100 = 72.
What's the difference between a weighted and a simple average?
A simple average counts every item the same. A weighted one counts each item by how much it's worth, so a final worth 40% moves your grade far more than a 5% quiz.
What do I need on the final to pass?
Put your pass mark, say 60, in as the target and enter the final's weight. The calculator tells you the score you need on the exam.
Does this give letter grades?
No, every school draws its own lines. Check your syllabus, or use the GPA calculator to turn letter grades into points.