How is a weighted average calculated?

Multiply each value by its weight, add those products together, then divide by the sum of the weights: Σ(value × weight) ÷ Σ(weight).

How does a weighted average differ from a plain average?

A plain (arithmetic) average treats every value equally. A weighted average lets some values count more — it is identical to a plain average only when all the weights are equal.

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

No. Weights can be any numbers — they are normalised automatically by dividing by their total, so weights of 3, 2, 1 work the same as 50%, 33%, 17%.

Can I use a weighted average for my grades?

Yes. Enter each grade as a value and the percentage that component is worth as its weight. For example a 90 worth 40% and a 70 worth 60% gives (90×40 + 70×60) ÷ 100 = 78.

What happens if a weight is zero?

A value with a weight of zero is effectively ignored, since multiplying by zero removes its contribution. The result reflects only the rows that carry weight.

How many values can I include?

As many as you like. Use the Add row button to add more value-and-weight pairs, and the weighted mean recalculates instantly each time.

Is anything sent to a server?

No — the calculation happens entirely in your browser and no data leaves your device.

Weighted Average Calculator

Weighted average calculator

A weighted average (or weighted mean) gives some values more influence than others. Instead of treating every number equally, each value is multiplied by a weight that reflects its importance before everything is combined. It is how course grades work when an exam counts for more than a quiz, how a portfolio return blends holdings of different sizes, and how survey results account for sample sizes.

How it works

Multiply each value by its weight, sum those products, then divide by the sum of the weights:

weighted average = Σ(value × weight) ÷ Σ(weight)

The weights do not need to sum to 1 or 100 — dividing by their total normalises them automatically, so weights of 3, 2, 1 behave exactly like 50%, 33%, 17%. Add as many rows as you need and the result updates live in your browser.

Example

Say a course grade combines a quiz of 80 (weight 1), a midterm of 70 (weight 2), and a final of 90 (weight 3):

Component	Value	Weight	Value × Weight
Quiz	80	1	80
Midterm	70	2	140
Final	90	3	270

The weighted average is (80 + 140 + 270) ÷ (1 + 2 + 3) = 490 ÷ 6 = 81.67. A plain average of 80, 70 and 90 would be 80, so the heavier final pulls the result up.

Everything is computed locally in your browser — nothing is uploaded.