Weighted Mean Calculator

Calculate a weighted average when some values count more than others, such as course grades or portfolio returns.

Values and weights

One pair per line as value, weight. Weights can be percentages, credit hours, counts, or any positive numbers; they do not need to add up to 100. 3 pairs read.

Weighted mean

Ordinary mean for comparison: 84.3333

Value (x)	Weight (w)	Share	x × w
85	20	20%	1700
90	30	30%	2700
78	50	50%	3900
Total	100	100%	8300

x̄_w = Σ(x × w) ÷ Σw = 8300 ÷ 100 = 83

How to use this tool

Enter one pair per line as value, weight. Weights can be percentages, credit hours, counts, or any positive numbers.
The weights do not need to add up to 100. The calculator divides by their total.
Read the weighted mean, the ordinary mean for comparison, and the table showing each weight as a share.
Change a weight to see how much that value pulls the result.

Formula Reference

Weighted mean

x̄_w = Σ(xᵢ × wᵢ) ÷ Σwᵢ

Weight share

wᵢ ÷ Σw

Special case

Equal weights give the ordinary mean

ArticleWeighted and Geometric Mean ArticleMean, Median and Mode CalcGeometric Mean Calculator CalcDescriptive Statistics Calculator GlossaryGlossary: Weighted Mean

Frequently Asked Questions

What is a weighted mean?+

An average in which each value contributes in proportion to its weight. A final grade made of 20% coursework and 80% exam is a weighted mean of the two marks.

Do the weights have to add up to 1 or 100?+

No. The formula divides by the sum of the weights, so any positive weights work, and only their relative sizes matter. Weights of 2, 3 and 5 behave exactly like 20%, 30% and 50%.

How is it different from the ordinary mean?+

The ordinary mean treats every value equally. The two agree only when all weights are equal. Otherwise the weighted mean is pulled toward the values with the larger weights.

Can weights be zero?+

Yes. A value with weight zero has no effect on the result. Negative weights are not allowed.

Value (x)

Weight (w)

x × w

20%

1700

30%

2700

50%

3900

Total

100

100%

8300