Final Grade Calculator
The score you need on the final exam to end up with the grade you want.
The formula
needed = (target - current × (1 - w)) / w
where w is the final's weight as a decimal. Your course grade is a weighted average of what you've already earned and the final; this just solves that average for the unknown exam score. At 78% going in, wanting 80% with a 30% final: (80 - 78 × 0.7) / 0.3 = 84.7%.
The weight changes everything
The same jump costs a lot more when the final is small. Moving from 78% to 80% needs 84.7% on a 30% final, but 98% on a 10% final. If the number comes out above 100, the target isn't reachable through the exam alone; ask about extra credit or make peace with the closest reachable grade.