# Weighted average calculator: how to find an average when some values count more than others

> A plain average treats every number the same. A weighted average lets bigger or more important values count for more. This guide shows the formula, a worked example with course marks, how it differs from the simple average, and uses in grades, prices and portfolios.

Published 2026-10-09 by Toolcloak. 3 minute read. Original: https://toolcloak.pages.dev/articles/weighted-average-calculator-how-to-find-an-average-when-some-values-count-more-than-others
Related free tool: [Weighted Average Calculator](https://toolcloak.pages.dev/tools/weighted-average-calculator)

A **weighted average** is an average in which each value has its own weight, showing how much it counts. A final exam worth 50% should move your course mark more than a quiz worth 10%. A purchase of 500 units should move your average price more than a purchase of 20. The plain average cannot do that, and the weighted one can.

> **In short**
> - **Weighted average = sum of (value × weight) ÷ sum of weights.**
> - Marks of 85, 92 and 78 with weights 30, 50 and 20 give **87.10**.
> - The plain average of the same three marks is **85.00**. The weights pulled the result up, because the highest mark has the biggest weight.
> - Weights do not have to add up to 100. The formula divides by their total, so any positive numbers work.

## The formula, step by step

**Example: three marks with different weights**

1. **Multiply each value by its weight.** 85 × 30 = **2,550** · 92 × 50 = **4,600** · 78 × 20 = **1,560**
2. **Add the products.** 2,550 + 4,600 + 1,560 = **8,710**.
3. **Add the weights.** 30 + 50 + 20 = **100**.
4. **Divide.** 8,710 ÷ 100 = **87.10**.

*Type one item per line as the value and then the weight, such as 85 30. The tool shows the weighted average, the total weight and the number of items.*

Try it: [Weighted Average Calculator](https://toolcloak.pages.dev/tools/weighted-average-calculator). Enter one value and weight on each line to get the weighted average.

## How each value contributes

| Mark | Weight | Contribution to the average | Share of the weight |
| --- | --- | --- | --- |
| 85 | 30 | 25.5 | 30% |
| 92 | 50 | 46.0 | 50% |
| 78 | 20 | 15.6 | 20% |

*The contributions add up to 87.10. The 92 carries half the weight, so it contributes about half of the result.*

**Weighted against plain average**

| Weighted average | Plain average |
| --- | --- |
| 87.10 | 85.00 |
| Weights 30, 50 and 20 | (85 + 92 + 78) ÷ 3 |
| The 92 counts for half | Every mark counts the same |
| Matches how a course is graded | Ignores how much each is worth |

*The difference is 2.10 points here. It can be much larger when the weights are very uneven.*

## When all weights are equal

If every weight is the same, the weighted average equals the plain average. Entering 85 1, 92 1 and 78 1 gives 85.00. So a plain average is just a weighted average with equal weights, and the weighted version is the more general tool.

## Uses beyond marks

- **Average buying price.** If you buy 50 units at ₹100, 30 at ₹120 and 20 at ₹90, the average price is (5,000 + 3,600 + 1,800) ÷ 100 = ₹104 per unit, not the plain ₹103.33 of the three prices.
- **Course and exam marks,** where each part has a stated weight.
- **Portfolio returns,** where each holding's return is weighted by how much is invested in it.
- **Survey scores,** where groups of different sizes are combined.
- **Ratings,** where a product with 500 reviews should count for more than one with 5.

**Average buying price, the same idea**

|  | Value | Note |
| --- | --- | --- |
| Weighted average price | ₹104.00 | Weights are the units bought |
| Plain average of prices | ₹103.33 | Ignores the units |
| Total units | 100 | The sum of the weights |
| Total spent | ₹10,400 | Sum of price × units |

*For prices and units, the weighted average is the price per unit you actually paid. The [Stock Average Calculator](https://toolcloak.pages.dev/tools/stock-average-calculator) uses the same idea.*

> **Check what the weights mean:** In a course, weights are shares of the final grade. In a purchase, weights are units. Do not mix them in one list. If a weight is zero, that value does not count at all, and negative weights are rejected by the tool.

## Using it well

1. **List each value** and write its weight next to it.
2. **Make sure the weights match one idea:** all shares, or all units.
3. **Run the calculator** and compare it with the plain average to see the effect of the weights.
4. **Check a result** by seeing if it falls between the lowest and the highest value. A weighted average always does.
5. **Use the weights to plan:** to lift the result, improve the values that carry the most weight.

## Frequently asked questions

### How do I calculate a weighted average?

Multiply each value by its weight, add the products, and divide by the sum of the weights. For 85, 92 and 78 with weights 30, 50 and 20, the result is 8,710 ÷ 100 = 87.10.

### Do the weights have to add up to 100?

No. The formula divides by the total of the weights, so they can add up to any positive number, such as 10, 100 or 1,000 units.

### What is the difference between a weighted and a simple average?

A simple average gives every value the same importance. A weighted average gives each value a weight, so some values count more.

### Can the weighted average be outside the range of the values?

No. With non-negative weights it always lies between the smallest and the largest value.

### How do I use it for course grades?

Enter each mark with the percentage the assessment is worth. If the weights do not add to 100 because some work is still to come, use the [Final Grade Calculator](https://toolcloak.pages.dev/tools/final-grade-calculator) to find the score you need.

### Is it the same as the average calculator?

The [Average Calculator](https://toolcloak.pages.dev/tools/average-calculator) treats every number equally. Use the [Weighted Average Calculator](https://toolcloak.pages.dev/tools/weighted-average-calculator) when the numbers carry different weights.