What this calculator does
Find the true average when some numbers count more than others. A weighted average gives some values more say. A final exam worth 50% of a course should count more than a quiz worth 10%. A 4-credit class should affect a GPA more than a 1-credit lab. And 200 shares bought at one price matter more than 10 bought at another. A plain average treats every value the same, so it gives the wrong answer in all of these cases.
Enter the values in one box and their weights in the other, in the same order. The weight is how much each value counts. The calculator multiplies each value by its weight, adds up the results, and divides by the total weight. It also shows the plain average to compare, and how much of the total weight each value carries.
Where it's used
Why this math matters outside the classroom:
- Course grades. A class weighting homework 20%, quizzes 30% and the final 50% turns scores of 90, 80 and 70 into 0.2 × 90 + 0.3 × 80 + 0.5 × 70 = 77.
- GPA. A student with an A (4.0) in a 4-credit class and a B (3.0) in a 3-credit class has a GPA of 25 ÷ 7, about 3.57.
- Average cost. A store that bought 100 units at $4 and 300 at $5 has an average cost of 1,900 ÷ 400 = $4.75 per unit.
- Portfolio returns. A portfolio 60% in a fund returning 8% and 40% in one returning 3% earned 0.6 × 8 + 0.4 × 3 = 6%.
- Star ratings. A product with 50 five-star and 10 one-star reviews averages (250 + 10) ÷ 60, about 4.33 stars.
How to use it
- Type the values, separated by commas, spaces or new lines. You can paste a column from a spreadsheet.
- Type the weights in the same order, one for each value. Percents, credits, counts and any other numbers of zero or more all work.
- Read the weighted average. Then open the table to see each value's share of the total weight.
What the inputs mean
- Values
- Any numbers: scores, prices, ratings or measurements. Negative numbers are allowed. Leave out the commas in large numbers, like 1,000.
- Weights (same order)
- The weights don't need to add up to 100 or to 1, because the calculator divides by whatever they total. A weight of 0 leaves that value out. Weights can't be negative.
Formula and method
weighted average = (x1 × w1 + x2 × w2 + … + xn × wn) ÷ (w1 + w2 + … + wn) share of value i = wi ÷ (w1 + w2 + … + wn) with equal weights, the weighted average equals the plain average
In the formulas, x1, x2 and so on are your values, and w1, w2 and so on are their weights. n is how many values you have. i stands for any one of them, so wi is the weight of value number i.
Each value is multiplied by its weight, so a value with twice the weight counts twice as much. Dividing by the total weight brings the result back to the same units as your values. That's why the weights can be on any scale. Weights of 30, 50 and 20 give the same answer as 0.3, 0.5 and 0.2.
The weighted average always falls between the smallest and largest values that have a weight above zero. It's pulled toward the values that carry the most weight.
Worked example
A course grade is 30% homework, 50% exams and 20% a project. The scores are 90 for homework, 85 for exams and 78 for the project.
- Homework: 90 × 30 = 2,700.
- Exams: 85 × 50 = 4,250.
- Project: 78 × 20 = 1,560.
- Weighted sum: 2,700 + 4,250 + 1,560 = 8,510.
- Total weight: 30 + 50 + 20 = 100.
- Weighted average: 8,510 ÷ 100 = 85.1.
Result: The course grade is 85.1. That's a little above the plain average of the three scores (84.33), because the exam score carries half the weight.
Understanding the result
Compare the weighted and plain averages. If the weighted one is higher, the values that count most are above the rest. If it's lower, they're below. A large gap means the weights matter a lot to the result.
The share column shows how much each value can move the result. A value with a 50% share moves the average by half a point for every point it changes.
Assumptions and limitations
- Each weight belongs to the value in the same position in the list.
- Weights are zero or more, and at least one is above zero.
- For a grade that's still in progress, leave out any categories with no scores yet. The result is then your average so far. The final grade calculator can show what you need on the remaining work.
- Averages of rates, such as average speed over trips of different lengths, need the right weights: the distances or the times. Weighting by the wrong amount gives a misleading answer.
- It takes up to 1,000 values.
Frequently asked questions
Do the weights have to add up to 100%?
No. The calculator divides by the total of the weights, whatever it is. Weights of 3, 4 and 2 credits, or 30, 50 and 20 percent, or 0.3, 0.5 and 0.2, all work as you enter them.
How do I calculate a weighted GPA?
Enter each course's grade points as the values, for example 4.0, 3.0 and 3.7. Enter its credit hours as the weights, such as 3, 4 and 2. The result, 3.49 in this case, is your GPA weighted by credits. The GPA calculator can convert letter grades for you.
What is the difference between a weighted average and a plain average?
A plain average adds the values and divides by how many there are, so each one counts the same. A weighted average multiplies each value by how much it counts first. When all the weights are the same, the two give the same answer.
How do I find the average price of shares bought at different prices?
Use the prices as the values, and the number of shares bought at each price as the weights. The weighted average is your average cost per share. That's the total you spent divided by the total number of shares.
How this calculator is checked
Method: Standard definition of the weighted arithmetic mean. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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