Grade Calculator
Calculate a weighted grade from score and weight percentage rows, such as quizzes, projects, and exams, with a full contribution breakdown and steps shown.
The weighted grade formula
A course grade is a weighted sum, not a weighted average: each item's score counts toward the final grade in proportion to its weight percentage, and the weights are designed to add up to 100% on their own.
Multiply every item's score by its weight (as a percentage, divided by 100) to get that item's contribution. Add up every contribution — the result is the overall grade, on the same 0–100 scale as each individual score.
Worked example
Three graded items: a quiz worth 20% of the grade (scored 85), a project worth 30% (scored 90), and a final exam worth 50% (scored 78).
- Contribution per item: 85 × 20 / 100 = 17, 90 × 30 / 100 = 27, 78 × 50 / 100 = 39
- Sum the contributions: 17 + 27 + 39 = 83
- Check the weights: 20 + 30 + 50 = 100% — the weights add up cleanly, so 83 is the final course grade.
When the weights don't sum to 100%
Suppose a quiz worth 50% (scored 80) and a project worth 40% (scored 90) are entered, but a third graded item is missing:
- Contribution per item: 80 × 50 / 100 = 40, 90 × 40 / 100 = 36
- Sum the contributions: 40 + 36 = 76
- Check the weights: 50 + 40 = 90%, not 100%
The calculator still shows 76 as the exact weighted sum — it does not block the result — but it warns that the weights only total 90%, which usually means a category (like the missing final exam) hasn't been entered yet, or a weight was mistyped.
Common mix-ups
- Treating it as an average. Dividing the sum of contributions by the number of items (or by the total weight) turns this into the wrong formula — GPA-style weighted averages are for combining separate courses, not separate graded items within one course.
- Weights that don't sum to 100%. A typo (entering 2 instead of 20, or forgetting a category) throws off the total weight; the warning is there to catch this before you trust the grade.
- Mixing percentage and fraction weights. Enter weight as a percentage number (20 for 20%), not as a decimal fraction (0.2) — a weight of 0.2 contributes almost nothing compared to the intended 20%.
Where this shows up
Teachers and students use a weighted grade to combine quizzes, homework, projects, and exams into one course grade using each category's official weight. For combining separate courses into one overall academic average instead, see the GPA calculator; for computing what's needed on a remaining item to reach a target final grade, see the final grade calculator.
Frequently asked questions
- How do I calculate a weighted grade by hand?
- For each item (a quiz, project, or exam), multiply its score by its weight percentage and divide by 100 — that's the item's contribution to the final grade. Add up every item's contribution, and the total is the weighted grade. There is no division by a total weight, so this only gives a clean 0–100 result when the weights you enter add up to 100%.
- Why is this a sum and not an average?
- A weighted average (like GPA) divides the total by the sum of the weights, so it self-corrects even if the weights don't add up to a round number. A course grade, by contrast, is built from weights that are supposed to already sum to 100% (20% quizzes + 30% projects + 50% final, for example) — so the calculator just adds up score × weight/100 per item. If your weights don't sum to 100%, the sum is still computed exactly, but it no longer represents a clean 0–100 grade, so the calculator flags it with a warning instead of silently rescaling it for you.
- What happens if my weights don't add up to 100%?
- The calculator still computes and shows the weighted sum — it does not block the result — but it displays a warning noting your total weight so you can catch a typo (e.g. entering 20 instead of 2.0, or forgetting a category). Fix the weights so they sum to 100% if you want the result to represent a true percentage grade.
- Can I use this to combine quizzes, projects, and exams with different weights?
- Yes — enter one row per category (or per individual assignment) with its score and its weight percentage. As long as the weights across all rows sum to 100%, the total is your overall course grade on the same 0–100 scale as each individual score.
- What is the difference between this calculator and the GPA calculator?
- The GPA calculator computes a true weighted average (grade points weighted by credit hours, divided by total credits) for combining multiple courses into one number. This calculator computes a weighted sum (scores weighted by percentage) for combining multiple graded items — quizzes, projects, exams — into one course grade. Use GPA across courses; use this calculator within a single course.
- Can a score be above 100 or a weight be entered as a decimal?
- Yes to both. A score above 100 (extra credit) is accepted and contributes proportionally more than a full score would. Weights accept decimals too (e.g. 12.5), as long as every weight is 0 or greater — they don't have to be whole numbers.