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Financial Planning

Purchasing Power Calculator

Adjust a sum of money between two periods using official price-index (CPI) values that you enter.

Your inputs

Use official index values from your national statistics office.

Results

Equivalent amount in the end period

$125.00

Cumulative price change
25%
Change in purchasing power of money
-20%

✓Exact calculation — rounded only for display

Inputs are never added to links for financial, salary or health calculators.

What this calculator does

Price indexes such as the consumer price index track the cost of a basket of goods over time. Comparing two index values converts money from one period into equivalent money in another.

Formula and method

Equivalent amount = amount × (CPI end ÷ CPI start)

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Amount in the start period: 100 (any currency)
  • Price index (CPI) in the start period: 100
  • Price index (CPI) in the end period: 125

Results

  • Equivalent amount in the end period: 125
  • Cumulative price change: 25%
  • Change in purchasing power of money: -20%

How to read the results

If the index doubled, money buys half as much: the purchasing power change is −50 %.

Assumptions and limitations

  • Use index values from your national statistics office for the same index series and base year.
  • The defaults are illustrative, not real data.

Financial results are estimates based on the inputs and assumptions shown. They are not financial advice; confirm figures with your lender, provider or a qualified adviser before making decisions.

Questions

Why does this ask for index values?

So the result reflects official measured inflation for your country and period rather than an assumed rate.

Methodology and verification

Result type
Exact mathematical calculation (rounded only for display)
Formula version
1.0
Automated verification
2 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

Privacy

Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Because this calculator can involve personal financial or health details, your inputs are never added to share links or saved to history. Privacy policy