How the required score is worked out
Your current grade already reflects everything counted so far, which together make up the portion of your grade the final does not cover. The formula rearranges the weighted-average equation to solve for the missing piece: required exam score = (target − current × (1 − weight)) ÷ weight. In plain terms, it figures out how much of your target still has to come from the final, then divides by the final's weight to convert that into an exam percentage.
Reading the result
The headline number is the score you need on the final to hit your target exactly. If it comes out at zero or below, you've already locked in the grade — even a blank exam keeps you at or above target. If it comes out above 100%, the target isn't reachable with a normal exam, and you'd need extra credit or a lower goal. The tool spells out which of these situations you're in so there's no ambiguity.
Why the final's weight is decisive
The weight of the final determines how much leverage the exam has. When the final is worth a lot — say 40% — a strong or weak performance swings your grade dramatically, for better or worse. When it's worth little — say 10% — even a perfect final can only nudge your grade a few points, which is worth knowing before you over- or under-invest your study time. Enter the weight exactly as your syllabus states it.
A worked example
Say your current grade is 88%, the final is worth 30%, and you want to finish with a 90%. The calculator returns about 94.7% — reachable but demanding. Drop the target to a B (80%) and you'd only need about 61.3%; aim for an A (90%) and it's that 94.7%. If your current grade were 95% instead, you could score as low as about 78% on the final and still land your 90%.
Tips for exam planning
Use the target table to weigh effort against reward: if locking in a B needs 60% but an A needs 95%, decide honestly which is worth the extra study hours. Confirm your true current grade from your syllabus's weighting rather than a rough average, and remember that this assumes the final replaces exactly the stated weight and everything else is already reflected in your current grade.