Smarter Than Free calculator
Purchasing Power Calculator: what inflation does to your money
See what inflation does to an amount of money over time. Real value today, percent lost, and how much you need later to match today. No live CPI feed: you pick the rate.
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Calculator
Purchasing power of 1 unit of local currency over time
What 1 unit from the base year is worth later (base = 1.00). World Bank CPI (2010 = 100). Missing years show as –.
| Country | 1970 | 1980 | 1990 | 2000 | 2010 | 2025 |
|---|---|---|---|---|---|---|
| 🇯🇵 JP · JPY | ¥1.00 | ¥0.42 | ¥0.35 | ¥0.32 | ¥0.33 | ¥0.28 |
| 🇩🇪 DE · EUR | €1.00 | €0.61 | €0.47 | €0.37 | €0.32 | €0.23 |
| 🇨🇦 CA · CAD | C$1.00 | C$0.46 | C$0.26 | C$0.21 | C$0.17 | C$0.12 |
| 🇬🇧 UK · GBP | £1.00 | £0.28 | £0.15 | £0.11 | £0.09 | £0.06 |
| 🇺🇸 US · USD | $1.00 | $0.47 | $0.30 | $0.23 | $0.18 | – |
Germany = DEM/EUR continuous CPI series (fixed conversion, no splice). EMU aggregate has no values here.
Source: World Bank WDI, Consumer price index (2010 = 100) FP.CPI.TOTL, CC BY 4.0. Data years: 1960-2025 (WDI updated 2026-10-08).
How do you calculate purchasing power after inflation?
Real value ≈ amount ÷ (1 + inflation)^years. Amount needed later = amount × (1 + inflation)^years.
Where does the historical CPI table come from?
World Bank WDI consumer price index (FP.CPI.TOTL, 2010 = 100), CC BY-4.0. Missing years are shown, not filled in.
Does this use a live inflation feed?
The forward calculator uses the rate you type. The historical table uses the World Bank annual CPI extract cited below.
The formula
Future real value (in today money) = amount ÷ (1 + inflation)^years Purchasing power lost (%) = (1 − real ÷ amount) × 100 Amount needed later to match today = amount × (1 + inflation)^years Years until purchasing power halves = ln(2) ÷ ln(1 + inflation) inflation is a decimal (3% = 0.03). Same maths as discounting; the villain is called CPI when official.
Worked example
£1,000 left under the mattress at 3% inflation for 10 years.
Real value = 1000 ÷ (1.03)^10 ≈ £744.09 in today money.
Purchasing power lost ≈ 25.6%.
To buy what £1,000 buys today, you will need ≈ £1,343.92 in 10 years.
Halving time = ln(2) ÷ ln(1.03) ≈ 23.45 years.
Rule of 72 napkin check: 72 ÷ 3 = 24 years. Close enough for a pint; use the exact figure for a plan.
Methodology
How it calculates
- Forward calc deflates (or inflates) cash at the inflation rate you type.
- Historical table uses World Bank annual CPI index levels; missing years are shown, never filled in.
Formula
Future real value (in today money) = amount ÷ (1 + inflation)^years Purchasing power lost (%) = (1 − real ÷ amount) × 100 Amount needed later to match today = amount × (1 + inflation)^years Years until purchasing power halves = ln(2) ÷ ln(1 + inflation) inflation is a decimal (3% = 0.03). Same maths as discounting; the villain is called CPI when official.
Assumptions
- Forward calc uses your typed inflation rate, not a live CPI feed.
- Historical rankings exclude broken/gappy CPI series (see DATA_SOURCES.md).
Edge cases
- Halving time uses ln(2) ÷ ln(1 + inflation).
Sources
Last checked:
FAQ
Is this the same as present value?
Same compounding maths, different story. Present value discounts a future cash amount. Purchasing power asks what a cash pile you already hold is worth after inflation eats it.
Which inflation rate should I use?
Your guess, a central-bank target, or a long-run average. This tool does not fetch CPI. Presets at 2%, 3%, 5% and 10% are starting points, not forecasts.
Does this include investment returns?
No. It is inflation alone. If your savings earn a return, compare that rate to inflation separately (real return ≈ nominal − inflation as a rough guide).
Why link to the rule of 72?
Halving purchasing power is the twin of doubling prices. Same ln(2) idea. The rule of 72 page has the shortcut table.
Sources
Rates, rules or specs last checked 1 Nov 2026. Confirm on the official page before you act.
Not financial advice. This calculator is for education only. Double-check results before you make money decisions. Past moves do not predict future ones.