Weighted Average Calculator
Find a weighted average from values and their weights, useful for grades, prices, and scores.
Enter at least one value and its weight to see the weighted average.
How to use the weighted average calculator
Each row takes a value and its weight. Type both, add more rows with the button, and the weighted average updates as you go. Weights can be percentages, credit hours, dollar amounts, or any numbers that show how much each value counts.
A weighted average gives some values more pull than others. If every value should count the same, you want a plain mean instead, which the average calculator handles.
How a weighted average works
Multiply each value by its weight, add those products, then divide by the total of the weights. So a grade of 90 worth 40 percent and a grade of 80 worth 60 percent gives 84, not 85, because the lower grade carries more weight.
Only the relative size of the weights matters. Weights of 40 and 60 give the same result as 4 and 6, or 2 and 3. The tool shows the total weight alongside the answer so you can check it. To compare two single values as a percentage, the percentage difference calculator is the right tool.
Choosing your weights
Weights describe importance. For a course grade, the weights are the percentage each assignment counts toward the final mark. For a stock portfolio, the weights are the amount held in each position. For a survey, they might be the number of responses behind each score.
Pick whatever measures how much each value should count, and keep the unit the same across rows. Weights must be zero or positive. A value with a weight of zero is simply ignored. To track a yearly growth rate instead of an average, the CAGR calculator covers that.
Where a weighted average helps
Students work out a course grade from assignments that count for different shares. Investors find the average cost of shares bought at different prices. Shoppers blend unit prices across different pack sizes.
Any time the values do not all count equally, a plain average misleads and a weighted one is right. To see how much one figure moved from another over time, the percentage change calculator gives the rise or fall.
Frequently asked questions
- How do I calculate a weighted average?
- Multiply each value by its weight, add up those products, then divide by the sum of the weights. For example, 90 at weight 0.4 and 80 at weight 0.6 gives 84.
- What is the difference from a normal average?
- A normal average treats every value equally. A weighted average lets some values count more than others, based on the weight you give each one. They match only when all the weights are equal.
- What can I use as weights?
- Any non-negative numbers that show how much each value counts: percentages, credit hours, quantities, or dollar amounts. Only the relative size matters, so 40 and 60 work the same as 2 and 3.
- Do the weights need to add up to 100?
- No. The tool divides by the total of the weights, so any positive total works. Weights of 3, 4, and 2 are just as valid as percentages that sum to 100.
- What if all the weights are zero?
- Then the total weight is zero and the average is undefined, since it would divide by zero. The tool asks you to give at least one value a weight above zero.