Calculate your course grade by weighted categories or total points, then find out exactly what score you need on what's left to hit your target. Just need a quick "what do I need on my final" answer? Try the simpler What Do I Need on My Final? calculator.
Most syllabi use weighted categories (Homework 20%, Exams 50%, Final 30%). Some classes just add up total points earned instead — pick whichever matches your class. Not sure which one yours uses? See Points-Based vs. Weighted Grading.