What is a weighted average?

A weighted average is a type of mean where each value is multiplied by a weight that reflects its relative importance. The result equals the sum of (value times weight) divided by the sum of all weights. Unlike a simple average, a weighted average allows some values to count more than others toward the final result.

What is the difference between percentage mode and points mode?

In percentage mode, weights represent the share of the total (e.g., an exam worth 40% of your grade). All weights should add up to 100% for a fully defined weighting. In points mode, weights are arbitrary counts or quantities (e.g., a 200-point exam versus a 50-point quiz). The calculator divides by the total weight automatically in both cases, so the formula is identical — only the interpretation of weight values differs.

How is a weighted average different from a simple average?

A simple average treats all values equally. A weighted average assigns different importance to each value. For example, if you score 90 on a homework worth 10 points and 60 on a final worth 100 points, the simple average is 75 but the weighted average is (90x10 + 60x100) / (10 + 100) = 62.7. The weighted average reflects that the final exam counted much more.

When should I use a weighted average?

Use a weighted average whenever items do not contribute equally to the total. Common uses include: calculating course grades where assignments have different point values, computing portfolio returns where each asset has a different allocation, finding the average price paid across multiple purchase quantities (cost basis), and aggregating survey scores where some respondent groups are larger than others.

What does 'contribution' mean in this calculator?

Contribution is the percentage of the final weighted average that each individual row accounts for. It is calculated as (value x weight) / (sum of all value x weight products) x 100. A row with a high value and a high weight will have a large contribution. Rows with zero weight contribute nothing regardless of their value.

Weighted Average Calculator

Add values and weights below. Results update as you type.

Weight mode:

Label (optional)	Value	Weight (%)	Contribution

Weights sum to 0% (not 100%). The weighted average is still calculated correctly, but check your weights.

Weighted Average

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Unweighted Average

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simple mean

Total Weight

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How the Weighted Average Calculator Works

A weighted average gives each value a different level of importance based on a weight you assign. This calculator lets you add as many value-weight pairs as you need, choose between percentage and points weight modes, and see both the weighted average and a plain unweighted average side by side so you can understand the impact of your weights.

The Weighted Average Formula

The weighted mean is calculated as:

Weighted Average = ∑(Value × Weight) ÷ ∑(Weight)

For example, suppose you have three exam scores with different weights:

Homework: score 85, weight 20%
Midterm: score 72, weight 30%
Final: score 90, weight 50%

Weighted average = (85 × 20 + 72 × 30 + 90 × 50) ÷ (20 + 30 + 50) = (1700 + 2160 + 4500) ÷ 100 = 83.6

The simple (unweighted) average of those three scores would be (85 + 72 + 90) ÷ 3 = 82.3. The difference occurs because the final exam carries the most weight.

Percentage Mode vs Points Mode

In percentage mode, each weight represents the share of the total that row contributes. All weights should ideally add up to 100% for a fully balanced weighting scheme, though this calculator works correctly even if they do not. This mode is typical for grade calculations where a syllabus specifies that homework counts for 20%, a midterm for 30%, and a final for 50%.

In points mode, each weight is a raw point value — such as the maximum possible points on each assignment. A 200-point final exam and a 50-point quiz use their point totals as weights directly. The calculation is mathematically identical; only the numbers you enter differ. This mode is common when a grade book uses total accumulated points rather than percentages.

Understanding Individual Contributions

Each row in the table shows its contribution to the final weighted average. This is the percentage of the total weighted sum that comes from that row alone. A row with a high score and a large weight will dominate the result. A row with a weight of zero contributes nothing regardless of its score. Reviewing contributions helps you understand which items drive your result and where improvement would have the most impact.

Common Uses for Weighted Averages

Academic grades: Most university courses assign different percentages to homework, quizzes, midterms, and finals. Entering each component as a row gives you your current weighted grade instantly.

Investment portfolio returns: Each holding contributes to your portfolio return in proportion to its allocation. If 60% of your portfolio is in stocks returning 10% and 40% is in bonds returning 4%, your weighted portfolio return is (10 × 60 + 4 × 40) ÷ 100 = 7.6%.

Average cost basis: When you buy shares at different prices and quantities, your average cost per share is a weighted average of price weighted by quantity. This is critical for accurate tax reporting.

Survey and poll aggregation: When combining results from different demographic groups of unequal size, applying population-based weights corrects for over- or under-representation of any group.

Supplier and vendor scoring: Businesses rank suppliers on multiple criteria such as price, quality, and delivery speed, each with a different importance weight. A weighted average of scores produces a single comparable number per vendor.

Tips for Accurate Results

When using percentage mode, verify that your weights sum to 100%. If they do not, this calculator will still compute a valid weighted average using whatever weights you provide — but the result may not match what you expect if you intended a full 100% distribution. The calculator shows a warning and the current weight sum so you can catch any discrepancy at a glance.

Labels are optional but highly recommended for anything beyond a quick calculation. Adding a label to each row makes the printout and shared URL readable at a glance, especially when sharing calculations with classmates, colleagues, or clients.

Frequently Asked Questions

A weighted average is a type of mean where each value is multiplied by a weight that reflects its relative importance. The result equals the sum of (value × weight) divided by the sum of all weights. Unlike a simple average, a weighted average allows some values to count more than others toward the final result.

In percentage mode, weights represent the share of the total — for example, an exam worth 40% of your grade. All weights should add up to 100% for a fully defined weighting. In points mode, weights are raw point counts — for example, a 200-point final versus a 50-point quiz. The calculation is mathematically identical; only the interpretation of the weight values changes.

A simple average treats all values equally. A weighted average assigns different importance to each value. For example, scoring 90 on a 10-point homework and 60 on a 100-point final gives a simple average of 75, but a weighted average of (90 × 10 + 60 × 100) ÷ 110 = 62.7. The weighted average reflects that the final exam counted much more toward the total.

Use a weighted average whenever items do not contribute equally to the total. Common uses include calculating course grades with different assignment weights, computing investment portfolio returns by allocation, finding the average cost basis of shares bought at different prices and quantities, and aggregating survey scores where some groups are larger than others.

The contribution column shows what percentage of the final weighted average each row accounts for. It equals (value × weight) divided by the total weighted sum, multiplied by 100. A row with a high value and high weight will show a large contribution percentage, indicating it has the strongest influence on the final result.