How to use the calculator
Write one item per line: the value first, then a space, then its weight. A course grade of 85 worth 4 credits is 85 4. Weights can be anything that says how much an item counts — credit hours, percentages of the final grade, hours worked, units bought. If no line has a weight, every value counts once and you get an ordinary average. You can paste two columns straight from a spreadsheet: tabs work as separators too.
The two optional scale fields convert the result. Put the top of your grading scale in the first (100, 30, 20…) and the scale you want in the second: an average of 85.5 out of 100 becomes 8.55 out of 10. The target fields answer the most common follow-up question — what do I need on the next test, course or exam to bring my average to a given number?
The formula
Weighted average = Σ(value × weight) ÷ Σ(weights). Multiply each value by its weight, add the products, and divide by the sum of the weights. When all weights are equal this collapses to the plain average, which is why a list without weights still works.
The value you need on one more item of weight w to reach a target T is (T × (W + w) − S) ÷ w, where S is the current sum of products and W the current total weight.
Worked example: four courses
| Course | Grade | Credits | Grade × credits |
|---|---|---|---|
| Biology | 92 | 3 | 276 |
| Calculus | 85 | 4 | 340 |
| History | 78 | 3 | 234 |
| Spanish | 88 | 2 | 176 |
| Total | 12 | 1,026 |
1,026 ÷ 12 = 85.5. The simple average of the four grades is 85.75: it is a little higher because the 78 in a 3-credit course weighs more than the 88 in a 2-credit one. Weighting always pulls the result toward the items that count most.
Weighted grades by category
Many syllabi weight categories in percent: homework 20%, quizzes 30%, final exam 50%. With category averages of 90, 80 and 70 you type 90 20, 80 30 and 70 50 on three lines and get 77 — the heavy final exam drags the grade down even though the homework average is an A. Percent weights do not have to add up to 100: if only some categories are graded so far, the calculator divides by the weights you entered, which is exactly the "current grade" most online gradebooks show.
Other uses
- Average purchase price: 10 shares at $40 and 30 shares at $50 average $47.50, not $45 — type
40 10and50 30. - Average speed or rate: weight each speed by the time spent at it, not by the distance.
- University averages abroad: in Italy the exam average is weighted by CFU credits and converted to a starting graduation mark out of 110 (average × 110 ÷ 30) — use 30 and 110 in the scale fields.
- GPA: letter grades must first be turned into grade points; the GPA calculator does both steps.
Common mistakes
- Averaging averages. The average of two class averages is only right if both classes have the same weight; otherwise weight each by its size.
- Forgetting zero-weight items. An item with weight 0 is listed but does not change the result — use it for pass/fail courses that do not count.
- Mixing scales. Convert every value to the same scale before averaging (all out of 100, or all out of 4).
Frequently asked questions
What is the difference between a weighted and a simple average?
A simple average gives every value the same importance. A weighted average multiplies each value by its weight first, so items with more credits, a bigger share of the grade or a larger quantity move the result more.
Do the weights have to add up to 100 or to 1?
No. The formula divides by the sum of the weights, so 20/30/50, 0.2/0.3/0.5 and 2/3/5 all give the same weighted average.
How do I calculate the grade I need on the final exam?
Enter your current grades with their weights, then the average you want in "Target average" and the weight of the final in "Weight of the next item". The calculator solves (target × new total weight − current sum) ÷ final weight.
Can I paste data from Excel or Google Sheets?
Yes. Copy two adjacent columns — values and weights — and paste them into the box. Each row becomes a line, and the tab between the cells is read as a separator.
Last updated: October 14, 2026