Weighted Average Calculator

A weighted average is the number you get when some values in a data set count for more than others. It shows up constantly, in class grades where a final exam outweighs a quiz, in stock portfolios where a bigger purchase pulls the average price toward it, and in financial ratios like the cost of capital a company pays across debt and equity. This calculator lets you enter your own values and weights and get the correct result right away, along with a plain average shown next to it for comparison. Type your numbers into the boxes above and the tool takes care of the rest.

What Is a Weighted Average?

A weighted average is a type of mean where each value is multiplied by an importance factor, called a weight, before the values are combined. This is different from a plain average, where every number counts the same no matter how important it actually is. Think about a course where the final exam is worth far more than a single homework assignment. Adding the two scores together and dividing by two would treat them as equally important, which is not how your grade actually works. A weighted average corrects for that by giving the final exam its proper share of the result.

What Is the Weighted Average Formula?

Written out in words, the formula is straightforward. You multiply each value by its own weight, add all of those products together, and then divide the total by the sum of the weights.

(Value 1 × Weight 1) + (Value 2 × Weight 2) + ... , all divided by (Weight 1 + Weight 2 + ...)

The value is the number you are averaging, such as a test score or a share price. The weight is how much that number should count toward the final result. The part on top tells you how much each value contributes once its weight is applied, and dividing by the total weight brings the answer back down to a scale you can compare against your original numbers.

What Do Value and Weight Mean in the Formula?

It helps to be clear about what these two words actually mean, since people mix them up more often than you'd expect. The value is simply the number you want to average, a grade, a price, a measurement. The weight is not a physical weight at all. It is a stand in for how much that value should influence the final answer, and it can be written in more than one format.

Whichever format you use, the calculator handles the scaling for you, so a set of weights written as 40 and 60 gives you the same result as 0.4 and 0.6.

How Do You Calculate a Weighted Average Step by Step?

1. List every value you want to include, whatever they represent, test scores, prices, or measurements.

2. Write down the weight that goes with each value, using whichever format matches the numbers you already have.

3. Multiply each value by its own weight, one line at a time, so you don't lose track of which weight belongs to which value.

4. Add up all of the results from the step above, then divide that total by the sum of all the weights. This last division is the step people forget most often when doing the math by hand.

Enter these same numbers into the calculator above and you'll see each of these steps broken down automatically.

What Is a Worked Example of a Weighted Average Calculation?

Say a course grade is split between homework, a midterm, and a final exam, and each one carries a different weight.

Add the three weighted scores together (17.0 + 23.4 + 46.0 = 86.4), and since the weights already add up to 100 percent, that total is the final weighted average, 86.4. Notice how the final exam, at half the grade, ends up shaping the outcome far more than the homework score does, even though the homework score itself was higher.

How Does This Weighted Average Calculator Work?

The calculator above follows the same logic as the manual steps just described, only faster. Enter a value in one box and its matching weight in the box next to it, add as many rows as you need, and press calculate. Alongside the weighted average, the tool also shows the plain average of the same numbers, so you can see at a glance how much of a difference the weighting actually makes.

Do the Weights Need to Add Up to 100 Percent?

No. Because the formula divides by the total of all the weights, the calculator gives the correct answer whether your weights add up to 100, to 1, or to something else entirely.

For example, if homework is worth 300 points out of a possible 500 combined with the exam, and the exam is worth 200 points, you can enter 300 and 200 directly as the weights. The calculator divides by their total, 500, on its own, so there's no need to convert anything into percentages first.

What Is the Difference Between a Weighted Average and a Simple Average?

A simple average treats every number in a data set as equally important. A weighted average lets some numbers count more than others. The difference becomes obvious once you look at an investing example.

A simple average of the two prices, $85 and $75, works out to $80. But the investor only bought 1 share at the higher price and 100 shares at the lower one, so the real cost per share, the weighted average, lands much closer to $75, since the larger purchase dominates the math. Use a simple average when every entry genuinely carries equal importance. Use a weighted average whenever some entries should count for more, whether that is because of size, credit hours, or how much was actually spent.

What Common Mistakes Cause a Wrong Weighted Average?

Mixing weight formats within the same calculation is one of the most frequent errors. Entering one weight as a percentage and another as a raw point value throws off the entire result, even when every individual number is correct. Dividing by the number of items instead of the total weight is another common slip, especially when the math is being done by hand rather than with a spreadsheet or calculator. And treating a score out of 20 the same as a score out of 100, without converting them to a common scale first, quietly changes the outcome without anything looking obviously wrong on the page. The calculator above avoids all three problems automatically, since it converts and divides correctly no matter which format you use to enter your numbers.

Where Do Weighted Averages Show Up in Everyday Calculations?

The same calculation appears in a few very different settings: grading in school, tracking the real cost of stock purchases, and estimating how much a company actually pays to finance itself. Each one uses the same core formula, just applied to a different kind of number. If one of these matches what you're working on, the sections below go into the specifics.

How Do You Calculate a Weighted Grade Average?

In school, each assignment category, homework, quizzes, a midterm, a final exam, carries a percentage weight set by the course syllabus. You multiply your score in each category by its weight and add the results together, the same way shown in the worked example above. If you also want to see what score you'd need on an upcoming assignment to hit a target grade, or want letter grades converted automatically instead of typing in numbers, the grade calculator is built specifically for that and includes those extra options.

How Do You Find Your Weighted Average Stock Cost?

When you buy the same stock more than once at different prices, your real cost per share is not the price you paid most recently. It is the weighted average of every purchase you've made, using the number of shares bought each time as the weight. This figure, often called your cost basis, is what brokers report for tax purposes and what you compare against the current market price to see whether a position is up or down. For a version of this calculation that also accounts for commissions and shows your unrealized gain or loss, the stock average calculator covers that in more detail.

What Is Weighted Average Cost of Capital (WACC)?

WACC is a specific business finance figure that blends the cost of a company's debt with the cost of its equity, weighted by how much of each the company actually uses. It's the same weighted average math covered throughout this page, just applied to a company's capital structure instead of grades or stock prices. If you need to work through that particular calculation, the WACC calculator walks through it step by step.

When Should You Use a Simple Average Instead?

A simple average is the right choice when every value genuinely deserves equal weight, daily temperatures across a week, say, or a set of test scores that all count the same toward a final grade. If that describes your situation, the simple average calculator skips the weighting step entirely and gets you straight to the answer.

How Do You Calculate a Weighted Percentage?

A weighted percentage is the same formula, just applied when both the values and the weights happen to be expressed as percentages, which comes up often in survey results or budget breakdowns. Say three departments make up different shares of a company's total spending, and each one reports a different percentage change year over year. Multiplying each department's change by its share of the budget, then adding the results, gives you the company wide weighted change. If your question is really about combining percentages rather than a full data set, the percentage calculator may be the faster tool for the job.

What Grade Do You Need on the Final Exam to Reach a Target Average?

This is really the same formula worked in reverse. Instead of solving for the final average, you already know the average you want and need to solve for the one missing score. Say you currently have an 85 percent average built from work worth 60 percent of your grade, and you want to finish with a 90 percent overall. The remaining 40 percent of your grade, the final exam, is what you need to solve for, and rearranging the formula gets you there. Doing that by hand gets tedious fast, so the final grade calculator is built specifically to solve for that missing number.

How Do Letter Grades Convert to a Weighted Average?

Many syllabi report each component as a letter rather than a number, so a grade like B+ needs to become its percentage equivalent, typically somewhere in the 87 to 89 percent range, before it can be multiplied by its weight.

If you're tracking a full semester rather than a single course, the GPA calculator takes letter grades directly and handles the conversion and credit weighting together.