Why your number differs from your gradebook

Short answer: usually neither of you is wrong. You are answering slightly different questions. Five differences explain nearly every mismatch, and four of them are settled by your syllabus rather than by arithmetic.

Work through them in order. The first is the biggest, and the one almost nobody checks.

1. Points-based and weighted courses disagree

These are two different grading systems, and on the same work they give different answers.

A course with two parts:

Points-based. Add everything up and divide once:

265 ÷ 300 × 100 = 88.3333…%

The calculator's Test score mode shows 88.33% — a B on a 90-for-an-A scale.

Weighted, 50/50. Convert each part to a percentage first, then weight them:

180 ÷ 200 × 100 = 90%
 85 ÷ 100 × 100 = 85%
90 × 0.50 + 85 × 0.50 = 87.5%

The Weighted grade mode shows 87.5%.

88.33% against 87.5%. Identical work, 0.83 percentage points apart, and on a 93-for-an-A scale that gap can sit across a letter boundary.

The reason is simple once you see it: in the points system, homework is 200 of 300 points, so it is really worth 66.7% of the course, not 50%. The points are the weights. Your strong homework counts for more.

So check which system your course uses. If your gradebook totals points, do not weight anything — use Test score on the running totals. If your syllabus has a weights table, use Weighted grade. Mixing the two is the most common source of a mismatch, and it is invisible unless you look for it.

2. Dropped scores

Many courses drop your lowest quiz, or lowest two. Your gradebook may already have done it, or may be waiting until the term ends.

Four quizzes — 95%, 88%, 72%, 64% — at equal weight:

• All four count: 25% each → 79.75%, a C.
• Lowest dropped: the remaining three at one-third each → 85%, a B.

More than five percentage points, and a whole letter, from one rule in your syllabus. If your gradebook shows 79.75% in week eight and you expected 85%, the drop has probably not been applied yet. That is a schedule difference, not an error.

To model this yourself, enter only the scores that count and give them equal weights that total 100. For three scores, use 33.333333, 33.333333 and 33.333334 — the weights must total exactly 100, so place the extra millionth on the last row.

3. Rounding, and when it happens

Two rounding decisions sit inside every grade, and courses answer them differently.

How many decimals? We display two. 89.6666… shows as 89.67.

Does rounding happen before the letter? Here, no. The letter is chosen from the unrounded percentage, so 89.5% is a B even though it displays as 89.5 and would round to 90. Many schools do round first, and then 89.5% becomes 90% and an A.

That single policy difference decides every grade within half a point of a boundary. It is written in your school's grading policy and nowhere else. If you are at 89.5%, it is the only document that matters.

4. Ungraded work is being counted — or not

A missing score is not a zero, and a zero is not a missing score. Gradebooks handle this inconsistently, and some let the teacher choose.

• Treated as zero, your grade looks worse than your work.
• Excluded from the calculation, your grade reflects only what is marked — which is why it can fall sharply when a big assignment finally gets entered.

This is also why "my current grade" is slippery when you plan a final exam. If your 83% already contains a placeholder zero for the exam, it is the wrong input. What grade do I need on my final exam? explains the number you actually need.

And if your syllabus weights total less than 100% because the term is not over, that has two honest fixes, which give different numbers.

5. Curves, extra credit and floors

Last, the adjustments no formula can see:

• A curve. Scores shifted or scaled against the class. Only your teacher has the class distribution.
• Extra credit. Added to one component's score, or to the final percentage, or as bonus points on the total — depending on the course. Each placement gives a different result.
• Grade floors or caps. Some courses set a minimum for a passing grade regardless of the arithmetic, or require the final exam to be passed on its own.
• Participation or attendance entered late, or at the teacher's discretion.

Each of these is a rule in a document. None of them is a calculation.

What to do when the numbers disagree

1. Check the system first. Points-based or weighted? This resolves most mismatches on its own.
2. Check what is included. Count the assignments in your gradebook against the ones in your calculation. A missing or extra row explains a lot.
3. Check whether the drop has been applied yet.
4. If you are within a point of a boundary, read the rounding policy. Do not estimate it.
5. Then ask your teacher. Bring the arithmetic: "I calculated 87.5% treating coursework and exam as 50/50 — does the course total points instead?" That is a question with an answer. "Why is my grade wrong?" is not.

Your gradebook is the record. Our calculator is a way of understanding it.

Next

• How do weighted grades work?
• From points to a percentage to a letter
• How this calculator works — our formulas and rounding, stated exactly so you can see where they would differ from yours.

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

Sources and checks

• All figures verified with the calculator in a browser on 16 October 2026.
• Points-based: 265/300 → 88.33% B; 180/200 → 90% A; 85/100 → 85% B. Weighted: 90@50, 85@50 → 87.5% B.
• Dropped quiz: 95@25, 88@25, 72@25, 64@25 → 79.75% C; [email protected], [email protected], [email protected] → 85% B. The plain average of 95, 88 and 72 is 85, which agrees.
• 44.75/50 → 89.5%, grade B — the unrounded-letter rule, read on screen.
• Rounding behaviour and the weights tolerance are read from the calculator's code.
• Gradebook policies on dropped scores, missing work, curves, extra credit and floors vary by school and course. This article states that they vary and names the variations; it does not claim any single policy, because no source could support one.