Buying Power Calculator
Buying power calculator works out Amount at the later price level and Increase in the amount from Base amount, Number of periods and Index at the starting date. The default figures on this page give amount at the later price level of 125.00; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
5 steps
- Cumulative price factor = end index / start index = 125 / 100 = 1.25.
- Amount at the later price level = 100 x 1.25 = 125.
- Total price change = (1.25 - 1) x 100 = 25%.
- The same 100 at the later price level buys 100 / 1.25 = 80.
- Rate per period = factor^(1/10) - 1 = 2.256518%.
Its 4 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
3 sources
Keep this result
Save it, change one figure, then compare the two
The calculation stays free. Save this scenario, adjust one assumption, save that too, and put them side by side to see exactly what the change costs you. A free account keeps 5 scenarios and 2 comparisons; Personal makes both unlimited and adds exports and private links. Nothing is saved unless you press Save.
What the buying power calculator calculates
Restates an amount of money at a different price level, either from an escalation rate per period or from two price-index readings, and reports the change, the annualised rate and the loss of purchasing power.
How to use this buying power calculator
Enter Base amount, Number of periods, Index at the starting date and Index at the later date. Amount at the later price level updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Amount at the later price level, Increase in the amount and Cumulative price factor.
The method follows Compound escalation, researched contract ESCALATION (Compound Cost Escalation Calculator), US Bureau of Labor Statistics, Consumer Price Index - Databases and calculation and US Bureau of Labor Statistics, CPI Inflation Calculator - how it works.
What you can compare
Change one input at a time to see how it affects Amount at the later price level, Increase in the amount and Cumulative price factor. The inputs you can vary are Base amount, Number of periods, Index at the starting date and Index at the later date.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
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Frequently asked questions
How do I calculate my buying power?
Restates an amount of money at a different price level, either from an escalation rate per period or from two price-index readings, and reports the change, the annualised rate and the loss of purchasing power. Open “How this is worked out” beside the result to see each step for your own figures.
How to calculate purchasing power?
It needs Base amount, Number of periods, Index at the starting date and Index at the later date. Nothing else is required, and the figures stay in your browser.
What information do I need for the buying power calculator?
You need Base amount, Number of periods, Index at the starting date and Index at the later date. The page opens with default figures that give amount at the later price level of 125.00, so you can see the scale before entering your own.
What does this buying power calculator show?
It shows Amount at the later price level, Increase in the amount, Cumulative price factor, Total price change, Rate per period (compounded), What the base amount still buys and Purchasing power lost, with the working and any warnings for your entries.
Can I check how the buying power calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.