Index Number Calculator
Calculate a simple price or quantity index number relative to a base period value.
Index Number
125.0000
Index Number vs Current Period Value
Formule
## How to Calculate an Index Number ### Formula **Index = (Current Value / Base Value) * Base Index** An index number expresses a value relative to a base period. The base period is typically set to 100. An index of 125 means a 25% increase from the base. Index numbers are used for price indices (CPI), stock indices, and economic indicators.
Exemple Résolu
A commodity priced at $125 today vs. $100 in the base year.
- 01Index = (125 / 100) * 100 = 125
- 02Change from base = ((125/100) - 1) * 100 = 25%
- 03The price is 25% above the base period.
Questions Fréquentes
What is the Consumer Price Index (CPI)?
CPI is a weighted index that measures the average price change of a basket of consumer goods over time. It uses a base year (index = 100) and tracks how prices evolve, serving as the primary measure of inflation.
What is the difference between a simple and weighted index?
A simple index uses a single item or unweighted average. A weighted index (like CPI) assigns weights based on relative importance or expenditure shares, giving a more accurate composite picture.
How do I change the base year?
To rebase an index from old base B1 to new base B2: New Index = (Old Index / Index at B2) * 100. This rescales all values so the new base period equals 100.
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