— Everyday Math
Weighted Average Calculator
Calculate a weighted average where some values count more than others. Enter values and weights to see the weighted result beside the plain average, useful for GPAs, course grades, weighted scores, and any mix where each item has different importance.
Weighted average
85.4
- Simple (unweighted) average
- 84.33
- Sum of weights
- 100
- Sum of value × weight
- 8,540
— Value, weight & contribution
| # | Value | Weight | Contribution | Share |
|---|---|---|---|---|
| 1 | 85 | 20 | 1,700 | 19.91% |
| 2 | 90 | 50 | 4,500 | 52.69% |
| 3 | 78 | 30 | 2,340 | 27.4% |
— Contribution breakdown
Download— How it works
Weighted average = Σ(value × weight) ÷ Σ(weights). For a GPA, that is Σ(grade points × credits) ÷ total credits. The weights can be raw numbers or percentages — the result is the same, because dividing by their sum normalises them.
When some values count more than others
A simple average treats every value equally. A weighted average does not: it lets each value carry an importance — its weight — so that the values that matter more pull the result towards them. You multiply each value by its weight, add those products up, and divide by the total of the weights. Because of that final division, the weights can be raw numbers, credits, or percentages that sum to 100; scaling them up or down does not change the answer. The calculator shows the simple, unweighted average next to the weighted one so you can see how much the weighting moved the result.
Worked example — scores 85, 90, 78 weighted 20%, 50%, 30%: Weighted = (85×20 + 90×50 + 78×30) ÷ 100 = 8,540 ÷ 100 = 85.4. The simple average is only 84.3 — the 90 pulls the weighted figure up because it carries the most weight.
GPA: the textbook weighted average
A grade point average is a weighted average where the values are grade points and the weights are credit hours — a high grade in a 4-credit course counts twice as much as the same grade in a 2-credit one. Turn on GPA mode and the calculator relabels everything in those terms: enter each course’s grade points and its credits, and it returns the GPA as Σ(grade × credits) ÷ total credits. The same toggle covers a weighted course grade, where the “credits” are the percentage each assignment, midterm or final is worth.
For example, a 4.0 in a 3-credit class, a 3.0 in 4 credits and a 3.7 in 2 credits gives (4.0×3 + 3.0×4 + 3.7×2) ÷ 9 = 31.4 ÷ 9 = 3.49 — lower than the plain 3.57 average of the three grades, because the 3.0 carries the most credits.
Reading the contributions
The table breaks the calculation open: for each item it shows the value, its weight, the contribution (value × weight) and that contribution’s share of the total. The shares reveal what is really driving the average — a value with a large weight dominates even if it is not extreme. The breakdown chart shows the same split visually. Two guards apply: the lists must pair up (the same number of values and weights, in order), and the weights cannot all be zero, since dividing by a zero total weight is undefined.
— Reader questions
How do I calculate a weighted average?
Multiply each value by its weight, add up those products, and divide by the sum of the weights. For scores 85, 90, 78 weighted 20, 50, 30: (85×20 + 90×50 + 78×30) ÷ 100 = 85.4. Enter the values and weights and the calculator does it instantly.
How is a GPA a weighted average?
A GPA weights each course’s grade points by its credit hours: GPA = Σ(grade points × credits) ÷ total credits. A grade in a higher-credit course counts more. Turn on GPA mode to enter grades and credits with the right labels.
Does it matter if my weights are percentages or raw numbers?
No. The weighted average divides by the sum of the weights, which cancels out any common scale — so weights of 20/50/30 give the same result as 2/5/3. Use whatever is natural; turn on “show weights as %” to see each as a share of the total.
How does a weighted average differ from a simple average?
A simple average treats every value equally; a weighted average lets some values count more. They match only when all the weights are equal. This calculator shows both, so you can see how much the weighting shifts the result.
Why must the values and weights match up?
Each value needs its own weight, paired in the same order, so the calculator multiplies the right value by the right weight. List the same number of each. Any pair where either entry is not a number is skipped.