Weighted Average Calculator
Calculate a weighted average from a list of values and their corresponding weights.
How to use the weighted average calculator
- Enter the values and their corresponding weights in the rows.
- The weights don't need to add up to exactly 1 or 100% — the calculator normalizes automatically.
- Add or remove rows as needed with the buttons.
How weighted average is calculated
A regular average gives every value equal weight. A weighted average lets some values count more than others, depending on their importance:
Worked example: scores of 80, 90 and 70 with weights of 0.5, 0.3 and 0.2 give 80 × 0.5 + 90 × 0.3 + 70 × 0.2 = 40 + 27 + 14 = 81. An ordinary unweighted mean would give (80 + 90 + 70) ÷ 3 = 80. The one-point difference arises because the highest score counts for less than the lowest one here — the weights shift the centre of gravity, and they should sum to 1.
A common example is a grade made up of several parts with different weighting — for example a final exam worth 50%, a project worth 30%, and an oral exam worth 20%. Another example is an investment portfolio where each holding's return is weighted by its share of the total portfolio.
Frequently asked questions
Do the weights need to add up to 100% or 1?
No. The calculator always divides by the sum of the weights you've entered, so the result comes out correctly whether the weights add up to 1, 100, or any other number — as long as they're proportionally correct relative to each other.
What's the difference between weighted and regular average?
A regular (arithmetic) average gives every value equal weight. A weighted average is identical to a regular average only when all the weights are equal — otherwise it gives more influence to the values with a higher weight.
Can weights be negative?
Mathematically, yes, but that rarely makes sense in practice. Most use cases (grades, portfolio shares, surveys) use positive weights that represent a share or an importance.