What grade do I need on my final?

The usual formula

Your course grade is your current grade at its share of the course, plus your final at its weight. Solving that for the final gives:

Write the weight as a decimal, so 40% is 0.40. Say your current grade is 85, the final is worth 40% and you want a 90:

1. What you’ve already earned: 85 × 0.60 = 51 points.
2. What’s still needed: 90 − 51 = 39 points.
3. Divide by the final’s weight: 39 ÷ 0.40 = 97.5.

You need 97.5 on the final. Use your current grade on the work graded so far, not counting the final. If your school’s portal counts ungraded work as zero, the grade it shows will be too low for this to work.

When the final replaces your lowest test

Some teachers let a high final replace your lowest test. The final then counts twice, which lowers the score you need.

Take a course with three tests, homework and a final, each worth 20%. Your tests are 65, 82 and 88, your homework is 90, and you want an 80.

• Without the replacement: all four grades count, for 65 points so far. You need (80 − 65) ÷ 0.20 = 75.
• With the replacement: the 65 drops out, leaving 52 points from the other three. The final now counts for 40%, so you need (80 − 52) ÷ 0.40 = 70.

Check that your answer is above the test it replaces. Here 70 beats 65, so the replacement really happens. If it doesn’t, the usual formula is the one that applies. The calculator checks this for you.

When you have several exams left

Treat the remaining exams as one block, using their combined weight. Say your current grade is 78 on half of the course, two exams are left at 20% and 30%, and you want an 80.

Together the exams are worth 50%, so you need (80 − 78 × 0.50) ÷ 0.50 = 82 on average across them, counted by weight. You don’t need an 82 on each, because a stronger first exam takes pressure off the second:

After the first exam, update your current grade and run the formula again. With a 75, your grade on the 70% of the course graded so far is (78 × 50 + 75 × 20) ÷ 70 = 77.14. The last exam then needs (80 − 77.14 × 0.70) ÷ 0.30 = 86.7, rounded up.

When you just need to pass

Use the passing mark as your target, and find it in your syllabus, because it varies. On the most common US scale a D starts at 60, but your program may require a 70 in the course.

With a current grade of 62 and a final worth 30%, that difference is large:

• To reach 60, you need (60 − 62 × 0.70) ÷ 0.30 = 55.4, rounded up.
• To reach 70, you need (70 − 62 × 0.70) ÷ 0.30 = 88.7, rounded up.

Some courses also set a minimum score on the final itself, whatever your overall grade. The formula can’t know about that rule, so check your syllabus for it.

When the answer is above 100 or below 0

A result above 100 means a perfect final won’t get you there. With a current grade of 70 and a final worth 25%, a target of 90 would take a 150. A 100 on the final leaves you at 77.5, so that’s the highest you can reach unless your course offers extra credit.

A result below 0 means you’ve already secured that grade. With a current grade of 95 and a final worth 20%, a target of 70 works out to −30. Even a zero leaves you at 76, as long as your course doesn’t require you to sit the final or pass it.

Common mistakes

• Using the wrong weight. Check the percentage in your syllabus, not the number of points on the exam.
• Counting on rounding. If you need a 90, don’t assume an 89.5 will be rounded up. Ask your teacher, or aim for the exact target.
• Using a letter as your target. Letter cut-offs vary between schools, so use your own course’s number.
• Forgetting other work. If a project is still ungraded, add its weight to the block you have left.