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LunaCalc

Math

Weighted Average Calculator

Calculate a weighted average from values and weights.

About this calculator

This weighted average calculator combines values with different weights, so heavier items influence the result more.

Formula notes

weighted mean = Σ(wᵢ·xᵢ) / Σ(wᵢ). Equal weights reduce it to the ordinary mean.

Worked examples

  1. Example: scores 80 (weight 3) and 90 (weight 1) give (240 + 90) / 4 = 82.5.
  2. Scores 80, 92, and 70 weighted 20%, 50%, and 30% give 80x0.2 + 92x0.5 + 70x0.3 = 83.

How to use it

  1. Enter each value together with its weight.
  2. Check that the weights reflect real importance.
  3. Read the weighted mean for grades, pricing, or ratings.

Frequently asked questions

Do the weights need to add to 100?

No. Only their relative sizes matter; the calculator divides by the total weight.

What if one weight is zero?

That item is ignored entirely, since it contributes nothing to numerator or denominator.

Limits and interpretation

  • Values and weights must correspond position by position, and the total weight cannot be zero.
  • Weights need not sum to 1 because normalization is possible, but negative weights change interpretation and may be inappropriate.

References