MATH · WEIGHTED AVERAGE
Weighted Average Calculator
Calculate the weighted average of any set of values. Add rows, enter each value and its weight, and get the exact Σ(v×w)/Σ(w) result with a per-row breakdown.
| Value | Weight | v × w | Weight % |
|---|---|---|---|
| 80 | 3 | 240 | 50% |
| 90 | 2 | 180 | 33.33% |
| 75 | 1 | 75 | 16.67% |
About This Calculator
A weighted average assigns a different level of importance — a weight — to each value before averaging. Unlike a simple arithmetic mean, a weighted average lets a high-weight item influence the result more than a low-weight item. Common examples include course final grades (exams count more than homework), investment portfolio returns, and survey responses with unequal sample sizes.
How It Works
Enter each value and its corresponding weight. The calculator filters out blank rows, validates that all weights are non-negative and sum to more than zero, and computes Σ(value × weight) / Σ(weight). A per-row breakdown table shows each contribution and weight percentage. The URL updates as you type so you can share or bookmark your inputs.
The Formula
Weighted Avg = Σ(vᵢ × wᵢ) / Σ(wᵢ)
- vᵢ
- each value in the set (may be negative)
- wᵢ
- the weight assigned to value vᵢ (must be ≥ 0)
- Σ(wᵢ)
- total weight (must be > 0)
Frequently Asked Questions
- What is the difference between a weighted average and a regular average?
- A regular average (arithmetic mean) treats every value equally — each contributes exactly 1/n of the result. A weighted average lets you assign a relative importance (weight) to each value so that higher-weight items pull the result toward them more strongly. If all weights are equal, the weighted average equals the arithmetic mean.
- Can I use fractional or decimal weights?
- Yes. Weights can be any non-negative real number, including decimals like 0.5 or 1.5. What matters is the ratio between weights, not their absolute scale — doubling every weight produces the same result.
- Can values be negative?
- Yes. Negative values are fully supported. The formula multiplies each value by its weight, so a negative value with a positive weight contributes a negative amount to the numerator. The total is then divided by the sum of weights.
- What happens if I leave a row blank?
- Fully blank rows (both value and weight empty) are silently ignored and do not affect the result. If you fill in only one field of a pair, the calculator asks you to complete or remove that row to avoid an unintentional mismatch.
- How many rows can I add?
- You can add between 2 and 25 rows. For datasets larger than 25 entries, consider a spreadsheet application. The minimum of 2 rows is enforced to keep the concept of a weighted average meaningful.