The Grade You Need On The Final Calculator

The formula this calculator uses

Needed on final = (Target - Current x (1 - Final weight)) / Final weight

current

Your standing before the final, as a percentage of the course so far

finalWeight

How much of the total grade the final exam is worth

target

The overall course grade you want to finish with

lockedIn

Current x (1 - finalWeight), the share of the grade already settled

How to check the result by hand

1. 1

   Write down the three numbers you already have

   Your current standing as a percentage, the weight of the final, and your target. For the worked case these are 82, 30 and 90. Convert each to a fraction — 0.82, 0.30 and 0.90 — and note that the coursework weight is 1 - 0.30 = 0.70.

2. 2

   Work out what is already locked in

   Multiply the standing by the coursework weight: 0.82 x 0.70 = 0.574. This share is settled and no exam performance can change it. At a 30 per cent weight it already represents 57.4 per cent of the final grade.

3. 3

   Subtract the locked-in share from your target

   0.90 - 0.574 = 0.326. This is the weighted amount the exam must still supply. Comparing it with the exam weight of 0.30 already shows that the target is slightly out of reach before any division is done.

4. 4

   Divide by the final's weight

   0.326 / 0.30 = 1.0866666666666667. If the result is at most 1 the target is reachable; if it exceeds 1 it is not, because no exam score is worth more than 100 per cent. Here it exceeds 1, so 90 is impossible from an 82 standing.

5. 5

   Compute the ceiling so the answer is useful

   Set the exam score to 1.0: 0.574 + 0.30 x 1.0 = 0.874, or 87.4 per cent. Reporting 87.4 as the highest achievable grade is far more useful than reporting a required 1.0866666666666667 that nobody can earn.