Weighted Index Calculator
Combine up to 4 values with their own weights into a single weighted average or index number, similar to how a price index is built.
Only the first this-many value/weight pairs are used (2 to 4 items).
Your results
Calculation breakdown
- Weighted average
- index = Σ(value × weight) / Σweight
Worked example
A price index made up of groceries (index 100, weight 0.4), housing (120, weight 0.3), transport (90, weight 0.2) and health (110, weight 0.1) gives a weighted index of about 106.
Assumptions
- Weights are automatically normalised by their total, so they don't need to add to exactly 1 or 100%.
- Weighted indices such as the CPI use official weights published by the ABS; this tool lets you test your own.
How this calculator works
Enter up to 4 values with matching weights (such as component prices and their basket shares). The calculator normalises the weights and returns the weighted average, alongside the simple average for comparison and an index expressed against a base of 100.
Frequently asked questions
Do my weights need to add up to 1 or 100%?
No, the calculator automatically normalises whatever weights you enter by their total, so relative proportions matter more than the exact numbers used.
How is this similar to the Consumer Price Index (CPI)?
The CPI combines price changes across categories using official expenditure weights; this tool applies the same weighted-average principle to any values and weights you choose.
What does the 'index vs simple average' figure show?
It compares your weighted result to an unweighted average of the same values, scaled so the simple average equals 100.