Finals week is stressful enough without guessing what score you need. One formula turns your current grade, the final weight, and your target grade into the exact score you must earn, and it also tells you when a target is impossible.
How it works
Required final score = (target grade – current grade x (1 – final weight)) / final weight, with weights as decimals. Current grade is your grade on completed work only. If the answer is above 100, the target cannot be reached even with a perfect final. If it is below 0, you already hold the target no matter what happens on the final. Your maximum possible grade = current grade x (1 – final weight) + 100 x final weight.
Step by step
- Find your current grade on completed work from your gradebook.
- Find the final exam weight from your syllabus as a decimal.
- Pick your target overall grade.
- Apply the formula above.
- If the result is above 100, lower the target or find extra credit, and compute your maximum possible grade.
- If the result is below 0, you already hold the target; focus on keeping it.
Worked example
Current grade 85 percent, final worth 30 percent, target 90 percent. Required = (90 – 85 x 0.70) / 0.30 = (90 – 59.5) / 0.30 = 30.5 / 0.30 = 101.7 percent. That is impossible, so 90 is out of reach. Maximum possible = 85 x 0.70 + 100 x 0.30 = 59.5 + 30 = 89.5 percent. For a target of 88 percent, required = (88 – 59.5) / 0.30 = 95 percent, which is hard but possible.
Common mistakes
- Using your grade including the final, or a guessed grade, instead of completed-work grade.
- Entering the final weight as 30 instead of 0.30, which breaks the formula.
- Ignoring dropped grades. Recalculate your current grade after dropping, before applying the formula.
- Assuming extra credit exists. Check the syllabus; many courses offer none.
Try it with the free tool
You can follow every step above by hand, but the free tool below does the same calculation instantly. Try your own numbers in it, then check one result by hand so you trust the method as well as the answer. Open the full tool here: open the tool.
Checklist before you finish
- Write down every input number first, with its unit, before you calculate anything.
- Work through the steps in order, and do not skip the unit conversions.
- Check the answer against the worked example above: is it the right size, and does the direction make sense?
- Round only at the end, and keep the unrounded figure for any follow-up calculation.
Practice with your own numbers
Pick three cases of your own and work each one by hand. First, try a simple round-number case you can check mentally. Second, try a realistic case with awkward numbers, the kind you will actually meet. Third, try an edge case, such as a very small or very large input, and confirm the answer still behaves sensibly. If any case gives a surprising result, re-check the units and the formula step by step before you trust it.
If your answer looks wrong
Most errors come from a small set of causes. Check that you used the same units throughout, that you divided where the formula divides and multiplied where it multiplies, and that you applied any percentage as a decimal. Check the order of operations: powers and brackets come before multiplication and division, which come before addition and subtraction. Finally, test the method on the worked example in this guide. If your method reproduces the example answer, the method is right and the inputs deserve a second look.
Quick tips
Run the formula for two targets: your dream grade and a safe grade. Study to the safe grade first, then push for the dream grade with the time that remains.