How this calculator works
A course grade with a final exam is a weighted average of the work already completed and the exam. If the exam is worth 40 percent, the earlier work is worth 60 percent. The current grade is the weighted average of that earlier work. Solving the weighted average for the exam score gives the score needed to reach a target: subtract the contribution already earned from the target and divide by the exam weight. A result above 100 percent means the target cannot be reached with this exam alone, and a negative result means the target is already secured even with a zero on the exam.
Formula
final course grade = current grade x (1 - weight) + exam score x weight. Required exam score = (target grade - current grade x (1 - weight)) / weight. Weight is entered as a percentage and converted to a fraction by the calculator.
Worked example
A current grade of 85 percent, a target of 88 percent and a final exam worth 40 percent require (0.88 - 0.85 x 0.60) / 0.40 = (0.88 - 0.51) / 0.40 = 0.925, or 92.5 percent on the exam. In the result mode, an exam score of 80 percent would give 0.85 x 0.60 + 0.80 x 0.40 = 0.51 + 0.32 = 83 percent for the course.
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Frequently asked questions
What if the required score is over 100 percent?
Then the target is out of reach with this exam alone. The calculator still shows the number so you can see how far off it is; you would need extra credit or a different grading arrangement. A negative required score means the target is already safe even if you score zero on the exam.
What does the current grade include?
It should be the weighted average of all graded work so far, after applying the earlier assignments own weights. If your course has several quarters, use the quarters weighted average as the current grade. Do not use a simple average of test scores unless every test carries the same weight.
Can the final exam weight be 0 percent?
A weight of zero would make the exam irrelevant and the required score undefined, so the calculator rejects it. If the exam is optional or can replace a lower earlier score, the course has a more complicated rule that a single weighted average cannot capture.
Does this account for extra credit?
No. Extra credit changes the current grade or adds points after the weighted average. Add the extra credit to the current grade first, or use the result mode and add the bonus separately. The calculator assumes the exam is scored out of 100 percent.