Home » Final Exam Weight Calculator (Work Out the %)

Final Exam Weight Calculator (Work Out the %)

Home › Grade Calculators › Final Exam Weight Calculator

Final Exam Weight Calculator

Teachers do not always say how much the final counts. If you know your grade before the final, your score on the final and your course grade afterwards, you can work the weight out exactly. The course grade after the final is a weighted average of the other two, so weight = (after − before) ÷ (final − before).

Worked example (the default): you had 86% going in, scored 72% on the final and finished with 82.5%. Weight = (82.5 − 86) ÷ (72 − 86) = −3.5 ÷ −14 = 0.25, so the final was worth 25% and everything else 75%. To check: 86 × 0.75 + 72 × 0.25 = 82.5.

Two cautions. First, if your exam score equals your earlier grade, the final cannot move your grade, so its weight cannot be found. Second, posted grades are often rounded, so a result like 19.6% or 24.7% usually means 20% or 25%. The method also assumes the final is the only thing that changed. If other assignments were added at the same time, the answer mixes their weight in. To find the score you need before the final, use the final exam grade calculator instead.

Result and step-by-step working

Final exam weight
25%

Everything before the final counted for 75%

  1. Weighted-average equation
    after = before × (1 − w) + final × w, so w = (after − before) ÷ (final − before).
  2. Substitute
    w = (82.5 − 86) ÷ (72 − 86) = −3.5 ÷ −14 = 0.25 = 25%.
  3. Check
    86 × 0.75 + 72 × 0.25 = 82.5%. If your teacher rounds the posted grades, the true weight can be a little different, so a result like 19.6% usually means 20%.

Frequently asked questions

How much is a final exam usually worth?
Commonly between 10% and 30% in high school and 20% to 40% in college courses, but the syllabus decides. Some courses use a points system instead of a percentage weight.
Why does the calculator say my numbers are impossible?
With a weighted average, the grade after the final must lie between your grade before and your exam score. If it does not, one of the numbers is off, or other grades changed at the same time.
Can I work out the weight without my grade before the final?
Not exactly. You need all three numbers. If the class uses points, use the final exam points calculator instead.
Does the weight change if I drop a quiz?
Yes. Any other change to your grade at the same time mixes into the result, so use numbers taken just before and just after the final was entered.

Related calculators

Last reviewed: October 9, 2026. Calculations run in your browser; nothing you enter is sent anywhere.

Scroll to Top