What if the weights don't add up to 100%?

Short answer: the calculator will not give you a final grade, and it is right not to. You have two honest fixes: fill in the missing component, or ask a narrower question about the work that is already graded. They answer different questions and give different numbers.

Enter weights that total 65% and the result panel says:

Check input — Weights total 65%. Adjust them to 100% to calculate a final grade.

Enter 110% and it says the same thing with 110% in it. No number appears.

Why no number

A weighted average over weights that do not sum to 100% is not a grade. It is a fragment.

If your weights total 65%, then 35% of your course is unaccounted for. Any "final grade" the calculator printed would be silently assuming something about that 35% — most likely that it does not exist, or that you scored zero on it. Both assumptions are wrong, and neither would be visible in the number.

So instead of a plausible wrong answer, you get the total you typed. The total is the diagnosis.

The usual cause: the term is not finished

Take a course graded like this:

Enter the three rows you have and the weights total 65%. Nothing is broken. You simply do not have a final grade yet, because you have not done 35% of the course.

Fix 1 — Add the missing component

If you know, or want to test, a score for the missing piece, enter it. Now the weights total 100% and the question becomes a real one.

Put the final exam in at 70% and 35% weight:

88 × 0.20 + 75 × 0.20 + 91 × 0.25 + 70 × 0.35
= 17.60 + 15.00 + 22.75 + 24.50
= 79.85%

The calculator shows 79.85%, letter C.

This is the fix you want when you are planning: try 70%, try 85%, try 95%, and watch the course grade move. It tells you what the exam is worth to you in the only unit that matters.

Looking for a specific course grade rather than trying numbers one at a time? The Final exam mode solves it directly — see what grade do I need on my final exam.

Fix 2 — Ask about the graded work only

Sometimes you do not want to guess. You want to know how you are doing so far, on the work that has actually been marked.

That is a different question, and it has a different formula. Divide by the weight you actually have instead of by 100:

grade so far = sum of (grade × weight) ÷ sum of weights
             = (88 × 20 + 75 × 20 + 91 × 25) ÷ 65
             = (1760 + 1500 + 2275) ÷ 65
             = 5535 ÷ 65
             = 85.1538…%

To get this from the calculator, scale each weight up so they total 100. Multiply every weight by 100 ÷ 65:

Enter those and the calculator shows 85.15%, letter B. That matches the long division above, to the two decimals the calculator displays.

Six decimal places is not fussiness. The weights have to total 100 within a very small tolerance, so round each one to six places and check the column adds to exactly 100.000000 before you trust the answer.

Read this number carefully. 85.15% is your standing on 65% of the course. It is not a prediction of your final grade, and it is not a grade your school recognises. It would only become your course grade if the remaining 35% happened to land on exactly 85.15% too.

Which fix do you want?

Both are correct. They are answers to different questions, 5.3 percentage points apart on identical work. If you report one while meaning the other, you will mislead yourself — usually in the comfortable direction.

When the total is more than 100%

A total of 110% is almost never your syllabus. It is almost always one of these:

• A typo. 30 typed where 3 was meant, or a weight entered twice.
• A duplicated row. The midterm entered under two names.
• Extra credit treated as a weight. Extra credit is usually added to a component's score, or to the final percentage, rather than taking a share of the course. Your syllabus decides which. Ours cannot.
• Points mistaken for weights. A 200-point homework total is not a 200% weight. Convert points to a percentage first with the Test score mode.

Read the total in the message, find the extra percentage points, and the cause is usually obvious within a line or two.

If your syllabus genuinely does not total 100%

It happens — a column that adds to 98%, or 105%. Do not quietly rescale it and move on. Ask your teacher which component is misprinted. The difference between a 98% column and a 100% column is a real difference in your grade, and only your school can say which number is the official one.

Next

• How do weighted grades work? — the base case, with the arithmetic.
• How this calculator works — the formulas, limits and rounding.

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

Sources and checks

• Both messages are quoted from the calculator's own output. Verified in a browser on 16 October 2026: three rows at 20/20/25 → "Check input", note "Weights total 65%. Adjust them to 100% to calculate a final grade."
• 88@20, 75@20, 91@25, 70@35 → displayed 79.85%, grade C. Verified in the browser, on phone and desktop.
• [email protected], [email protected], [email protected] → displayed 85.15%, grade B. Verified in the browser, on phone and desktop. Long division gives 5535 ÷ 65 = 85.153846…, which agrees.
• The weights-total tolerance and the refusal to calculate are read from the calculator's code.
• Extra-credit handling varies by school; this article states that it varies and does not claim a single rule.