インフレ 計算機 - Price and Purchasing Power
計算 inflation rate, annualized inflation, price change, and purchasing-power impact from initial and final values over time.
Enter a starting price, an ending price, and the number of years to calculate cumulative inflation, annualized inflation, and the change in purchasing power.
インフレ 計算機 - Price and Purchasing Power
計算 inflation rate, annualized inflation, price change, and purchasing-power impact from initial and final values over time.
About the インフレ 計算機
インフレ is the rise in a price index or in a specific price over time, and it quietly changes what a salary, pension, or cash balance can buy. People often quote a cumulative increase as if it were an annual rate, or they ignore the drop in purchasing power that is the mirror image of that increase. The inflation calculator separates those ideas: cumulative inflation, the constant annual rate that would produce the same change, and the percentage change in purchasing power.
Cumulative inflation is final value ÷ initial value − 1. Annualized inflation is (final ÷ initial)^(1/years) − 1, the geometric average. Purchasing-power change is 1 − final/initial, which is negative when prices rise. Optional start and end dates are for your records; the math uses the time-period field in years, so enter 5 rather than relying on the dates. Value change in currency units is also shown as final minus initial.
A price that moves from 100 to 110 over five years is 10.00% cumulative inflation but only about 1.92% a year. From 100 to 125 over ten years, cumulative inflation is 25.00% and the annualized rate is about 2.26%, while purchasing power falls 25.00%. That is why a “25% over a decade” headline overstates the yearly pace households actually felt.
CPI baskets, regional indexes, and quality adjustments can differ from the two prices you type. Hyperinflation, deflation, and mid-year timing are not seasonally adjusted here. Use official index values when you need a statistical inflation rate, and use this worksheet when you want the implied inflation between two known prices or balances.
Households can also run the inflation calculator on rent, tuition, or a grocery basket they actually buy, which often diverges from headline CPI. Businesses can apply it to a unit cost to see whether a planned price increase merely restores real margin. Because purchasing-power change is the negative of the cumulative price rise, a 25% price increase is a 25% loss of purchasing power on that item. Keep the year count honest; stretching a two-year jump across ten years will understate the annualized rate.
インフレ 計算機 Examples
These cases use cumulative inflation = final/initial − 1 and annualized inflation = (final/initial)^(1/years) − 1.
| Inputs | Cumulative inflation | Notes |
|---|---|---|
| Price 100 → 110 over 5 years | 10.00% | Annualized inflation is 1.92% and purchasing power falls 10.00%. |
| Price 100 → 125 over 10 years | 25.00% | Annualized inflation is 2.26% even though the decade change looks large. |
| Price 80 → 100 over 8 years | 25.00% | The same 25% cumulative rise annualizes to 2.83% over eight years. |
How to 計算 インフレ and Purchasing Power
- Enter the initial price or value and the later price or value in the same units.
- Enter the number of years between the two observations.
- Optionally record calendar dates; they do not replace the years field in the formula.
- Select Calculate to view cumulative inflation, annualized inflation, and purchasing-power change.
- Compare the annualized rate with a wage increase over the same years to see whether pay kept up.
インフレ 計算機 FAQ
Why is annualized inflation lower than cumulative inflation?
Cumulative inflation is the total change over the whole period. Annualized inflation is the constant yearly rate that compounds to that total, so a 10% rise over five years is only about 1.92% a year.
What does a negative purchasing-power change mean?
Prices rose, so a unit of currency buys less. If prices fall, purchasing-power change is positive and cumulative inflation is negative.
Do the optional dates change the result?
No. Years in the time-period field drive the annualized rate. Use dates only as labels for the scenario you are documenting.
Can I use CPI index levels instead of cash prices?
Yes, as long as both values are the same kind of index or price. The ratio is what matters, not whether the unit is dollars or index points.
Is this the CPI or the GDP deflator?
Neither is loaded automatically. The inflation calculator reports the implied inflation between the two numbers you supply, which you can take from any consistent series.