How do weighted grades work?

Short answer: each score is multiplied by its share of the course, and those products are added together. A weighted grade is not the average of your scores. It is the average of your scores after each one is scaled to how much the course says it counts.

The formula the calculator uses is one line:

final percentage = sum of (grade × weight ÷ 100)

A course, as your syllabus writes it

Most syllabi set this out as a short table. Say yours reads:

And say the term went like this: homework 92%, quizzes 78%, midterm 85%, final exam 88%.

The arithmetic, line by line

Each component contributes grade × weight ÷ 100:

Enter those four rows in the Weighted grade mode and the result reads 85.85%, letter B on the default A ≥ 90 scale. The note underneath confirms the weights total 100%.

Why it is not the average

The plain average of 92, 78, 85 and 88 is 85.75%.

The weighted grade is 85.85%. Ten hundredths apart — close enough to look like a rounding quirk, and that is exactly the trap. The two numbers agree here only because these four scores sit within 14 points of each other. When your scores are bunched up, almost any set of weights lands in the same place. Move the weight onto the score that is furthest from the rest and they part company fast.

Keep the same four scores and make the final exam worth 70%, with homework, quizzes and midterm at 10% each:

92 × 0.10 + 78 × 0.10 + 85 × 0.10 + 88 × 0.70
= 9.2 + 7.8 + 8.5 + 61.6
= 87.1%

Same term, same work, 87.1% instead of 85.85%, because the thing you did best on late in the term now carries most of the course.

The useful way to read your weights

Turn each weight into the damage a bad score can do.

In the first table, the 78% on quizzes is 22 percentage points below full marks, on 20% of the course. That costs 22 × 0.20 = 4.4 points of final grade. The 92% on homework is 8 points below full marks on 15% of the course, so it costs 8 × 0.15 = 1.2 points.

So the quizzes cost you nearly four times what the homework did — 4.4 points against 1.2 — even though the two scores are only 14 points apart. The damage a score does is not the score itself. It is the gap to full marks multiplied by the weight.

That is the practical reason to read your syllabus table at the start of the term rather than at the end. Both numbers in that multiplication are on it, so it tells you in advance which assessment you cannot afford to be careless with.

Two things that trip people up

Weights must total exactly 100%. If they do not, the calculator refuses to produce a number and tells you the total you entered instead. That is the correct behaviour, not a bug — see what to do when your weights do not add up to 100%.

Grades go in as percentages, not points. If homework is 180 points out of 200, convert it first: 180 ÷ 200 × 100 = 90%. Use the Test score mode for that, then carry the 90% into the weighted mode.

If your course is points-based instead

Some courses skip weights entirely and just total the points. Those two systems give different answers on the same work, and neither is wrong. Why your calculated grade can differ from your gradebook works through a course where the gap is nearly a whole letter.

Next

• Know your target and want to know what the final exam has to carry? What grade do I need on my final exam?
• Want the exact formulas and rounding rules? How this calculator works.

The result is a calculation, not an official grade. Your school's rules decide your grade.

Sources and checks

• Formula sum of (grade × weight ÷ 100) and the exact wording of the weights message: read from the calculator's code and confirmed on screen.
• Verified with the calculator on 16 October 2026, in a browser: 92@15, 78@20, 85@25, 88@40 → displayed 85.85%, grade B, note "Weights total 100%. Each component contributes its share."
• The 87.1% and the plain average of 85.75% are arithmetic on the same four scores, re-checked against the calculator's weighted mode.
• Default scale A ≥ 90, B ≥ 80, C ≥ 70, D ≥ 60, F ≥ 0 is the calculator's default and is editable. Real school scales differ; see the sources on how this calculator works.