What do I need on the final?
The two-in-the-morning question, answered honestly — including when the honest answer is that the grade you want is already out of reach.
How the math works
Your current grade covers everything except the final, so it carries whatever weight the final doesn't. If the final is worth 20%, your existing work is locked in at 80% of the total. The score you need is simply the goal minus what your existing work already contributes, divided by the final's weight — which is why a heavily weighted final can rescue a bad semester and a lightly weighted one mathematically cannot.
That division is also why the required score climbs so steeply when the final is worth little. Needing to raise your overall grade by 5 points with a 10%-weighted final means scoring 50 points above your current average; with a 40%-weighted final it's only 12.5 above. The weight, not your effort, sets how much is even possible.
The three scenario rows exist because the single "you need X" number hides the useful context. Seeing exactly where a 70% lands you often reframes the night: sometimes the difference between a frantic all-nighter and a solid night's sleep is one grade point that was never in reach anyway.
Questions
What if it says the grade isn't possible?
Then it isn't, with this final alone — and that's genuinely worth knowing before you burn a night. Look at what a realistic score does get you, check whether any extra credit or dropped-lowest policy exists, and aim at the grade that is reachable.
My class uses points, not percentages. Does this still work?
If your syllabus gives the final a percentage weight, yes. If everything is raw points, divide your earned points by points possible so far for the current grade, and the final's points by total course points for its weight.
Does this handle a dropped lowest test or extra credit?
Not directly — compute your current grade with those policies already applied, then enter that number here. Extra credit added after the fact effectively raises your current grade, so recompute it first.
Should I round the answer up?
Always round up, and add a couple of points of margin. Rounding rules, curve decisions, and one misread question all cut the same direction, and none of them cut in your favor.