Weighted Averages: When Values Do Not Count Equally
Calculate grades, prices, and returns without giving every value the same importance.
What it does and when to use it
A simple average assumes each observation matters equally. A weighted mean fits credits, quantities, or periods of different size.
What information to enter
Enter each value and its weight. Weights may be percentages, quantities, or points as long as the system is consistent.
How to understand the result
Large weights pull the result more strongly than small weights.
Recommended step-by-step workflow
- Check the assumptionsA simple average assumes each observation matters equally. A weighted mean fits credits, quantities, or periods of different size.
- Use matching unitsEnter each value and its weight. Weights may be percentages, quantities, or points as long as the system is consistent.
- Compare with another scenarioLarge weights pull the result more strongly than small weights.
Formula at a glance
Weighted mean = Σ(value × weight) ÷ Σ(weights)
Short example
A grade of 90 weighted 30% and 70 weighted 70% produces 76, not 80.
Common mistakes
- Forgetting to divide by the total weight.
- Mixing percentage and point weights without conversion.
Frequently Asked Questions
Must weights total 100?
No. The formula divides by total weight, though percentages are easy to verify.
When is a simple average enough?
When every value represents equal importance or equal quantity.
Are my personal inputs saved?
No. The calculators and guides are designed for quick browser use without storing your personal input values.