Weighted Average Calculator

A weighted average is a mean that accounts for the relative importance or frequency of each value. Unlike a simple average (which treats all values equally), a weighted average multiplies each value by its weight before summing, then divides by the total weight. The formula is: Weighted Average = Σ(Value × Weight) / Σ(Weight). For example, if a course has a midterm worth 30%, a final worth 40%, assignments worth 20%, and participation worth 10%, the weighted average grade correctly reflects the different importance of each component. Our weighted average calculator computes this for up to 20 items with optional labels.

1. 1. Enter Values and Weights: Type each value and its corresponding weight in the table. Labels are optional but help identify each item. Weights can be any positive numbers — percentages (30, 40, 20, 10), decimals (0.3, 0.4, 0.2, 0.1), or raw counts (300, 400, 200, 100). The weighted average calculator normalizes them automatically.
2. 2. Instant Calculation:Click "Calculate Weighted Average" and the weighted average calculatorcomputes the weighted mean, each item's contribution, and the comparison with the simple average. All processing happens locally in your browser — your data never leaves your device.
3. 3. Full Breakdown Displayed: The weighted average calculatorshows a detailed table with each item's weight percentage, contribution to the final average, and a visual bar chart. The full formula with all values is shown at the bottom.

• Simple Average: Treats all values equally — sum all values and divide by the count. Use when all items have equal importance or equal sample sizes. Formula: (v₁ + v₂ + … + vₙ) / n.
• Weighted Average: Accounts for different importance levels. Use when items have different weights, frequencies, or sample sizes. Formula: (v₁w₁ + v₂w₂ + … + vₙwₙ) / (w₁ + w₂ + … + wₙ).
• When they differ: If all weights are equal, the weighted average equals the simple average. They differ when weights are unequal — higher-weighted items pull the average toward their values. Our weighted average calculator shows both values and the difference between them.
• Weights don't need to sum to 100: Weights can be any positive numbers — percentages, raw counts, or arbitrary values. The weighted average calculator normalizes them by dividing by the total weight, so the result is the same whether you use (30, 40, 20, 10) or (3, 4, 2, 1) or (0.3, 0.4, 0.2, 0.1).

Each item's contribution to the weighted average is calculated as (Value × Weight) / Total Weight. The sum of all contributions equals the weighted average. This breakdown helps you understand which items have the most impact on the final result. For example, in a grade calculation, the final exam (weight 40%) with a score of 85 contributes 85 × 0.40 = 34 points to the weighted average. Our weighted average calculator shows this contribution for every item in the table, along with a visual bar chart for easy comparison.