Inflation Calculator
Calculate the current purchasing power of past amounts and average annual inflation.
Input Information
Result
The Inflation Calculator converts a past amount to its current monetary value and computes the average annual inflation rate. Using price indices, it shows the real change in purchasing power.
Term Glossary
- Price Index
- A measure of consumer price changes, expressed relatively with a base year set to 100.
- Purchasing Power
- The quantity of goods and services that currency can actually buy. When prices rise, purchasing power falls.
- Average Annual Inflation Rate
- The geometric mean of yearly inflation rates, representing the average pace of price increases over a period.
- 1
Enter the past amount
Type the amount whose purchasing power you want to trace.
- 2
Add both price indices
Look up past and current CPI on ECOS, keeping both from the same base-year series.
- 3
Set the elapsed years
Used for the annualized rate — the real gap between the two years.
- 4
Interpret the results
The equivalent figure answers the core question; the multiplier and annual rate serve comparisons.
Example — tracing 10,000 from five years ago (index 85 → 110)
- Equivalent today: 10,000 × 110/85 = 12,941 won for the same basket
- Cumulative change: (110−85)/85 × 100 = 29.41% over five years
- Annualized: (110/85)^(1/5) − 1 ≈ 5.29%
- Multiplier: 110/85 ≈ 1.2941x
Read the same numbers as money: 10 million left idle in cash now buys about 77% of what it once did (1/1.2941). Only investments beating the 5.29% annualized rate truly earned anything in real terms — that figure is your cash's break-even line.
Inflation Calculation Formulas
1. Present Value Conversion
2. Average Annual Inflation Rate
※ n = number of years elapsed
3. Purchasing Power Change Rate
💡 Inflation Calculator Tips
1. Compare Investment Returns Using Real Returns
Subtract the inflation rate from the nominal return to get the real return. For example, a 5% return with 3% inflation gives a 2% real return. Comparing investment performance adjusted for inflation is crucial.
2. Set Pension/Savings Goals in Real Value
1 billion won in 30 years has the purchasing power of roughly 400-500 million won today. Set pension/savings goals reflecting inflation.
3. Choosing the Right Price Index Matters
The Bank of Korea Consumer Price Index (CPI) is most commonly used. However, individual spending structures differ (food, housing, etc.), so perceived inflation may vary. GDP deflator and Producer Price Index provide more precise analysis.
QWhere can I find price index figures?
The Bank of Korea's ECOS system publishes annual Consumer Price Index series, as does Statistics Korea (KOSIS). Always pair indices from the same base-year series — mixing a 2020=100 series with a 2015=100 one throws every result off.
QWhy isn't the average annual rate just the arithmetic mean?
Prices compound, so the geometric mean is the correct average. A year up 10% followed by a year down 10% averages zero arithmetically, yet prices actually sit 1% below where they started (1.10 × 0.90 = 0.99). The formula used here — (current/past)^(1/n) − 1 — captures exactly that.
QHow do I use this for real interest rates?
Subtract expected inflation from nominal yield for an approximation of real return: a 3% deposit under 3% inflation preserves purchasing power but grows it not at all. The precise definition divides rather than subtracts, though the difference is negligible at low inflation. A negative real rate on long-term savings is your cue to revisit the strategy.
QOfficial numbers don't match what I feel at the store. Why?
CPI reflects the average urban household basket. Households heavy on dining out, or those whose housing costs jumped through a jeonse-to-purchase switch, will diverge from that average. Food categories often run hotter than headline inflation, fueling the gap between official figures and grocery receipts — tracking the subindices matching your own spending helps reconcile them.
QHow should long-term financial targets account for this?
Define goals in today's purchasing power, then gross them up by inflation before planning contributions. One hundred million won needed in 30 years under 3% inflation means accumulating roughly 242.73 million in future currency for the same real value. Inflate the target first, then plan toward the inflated number.