Convert an amount from one year into another using the consumer price index. Enter a sum, a starting year and a comparison year to see the equivalent value, the cumulative price increase, the average annual inflation rate, and how much buying power that money would have kept if you had simply held the cash. US data goes back to 1947 and Korean data to 1960.
The whole conversion is one ratio between two years' index values, so it does not matter that the two series use different base years (US 1982–84 = 100, Korea 2010 = 100). The base cancels out in the division.
Each year uses the annual average index. Prices differ between January and December, but a year-level question — 'what was $100 in 1990 worth' — is conventionally answered with the annual average.
US prices rose about 2.46 times between 1990 and 2025, an average of 2.61% a year. Korean prices rose about 3.03 times over the same period, or 3.22% a year.
A 2.46x price level means money kept its value at roughly 41%. One hundred 1990 dollars held as cash would buy about $41 worth of 1990 goods by 2025.
The CPI puts the goods and services households actually buy into one basket and tracks what that basket costs from year to year. The US Bureau of Labor Statistics prices a few hundred item categories; Statistics Korea prices roughly 460 items.
The index has no currency unit of its own. One period is set to 100 and every other period is expressed relative to it. The US series here uses the 1982–84 average as 100; the Korean series uses 2010 as 100.
Items are weighted by how much households spend on them. Housing and food move the index a lot because they take a large share of the budget, while a big swing in a minor category barely registers.
It reduces to a single line: converted amount = amount × (end-year index ÷ start-year index). If the price level doubled, the same basket costs twice as much. Nothing more is going on.
Take $100 from 1990 to 2025. The US index was 130.658 in 1990 and 321.962 in 2025. Dividing gives 2.464, so $100 × 2.464 ≈ $246.
The base year of each series is irrelevant to the answer because it cancels in the division. A table based on 2010 = 100 and one based on 1982–84 = 100 produce the same ratio.
Running it backwards uses the same formula — swap the two years and the ratio inverts. $246 in 2025 maps back to about $100 in 1990.
The cumulative rate answers 'how much did prices rise in total'. A ratio of 2.464 is (2.464 − 1) × 100 = 146% higher.
The annual rate answers 'what steady yearly rate would produce that'. Dividing 146 by 35 years gives 4.2%, and that is wrong: inflation compounds on the previous year's level, so it needs a geometric mean — (2.464^(1 ÷ 35) − 1) × 100 = 2.61%.
Compounding explains the gap. Applying 2.61% for 35 years lands exactly on 2.464, while 4.2% for 35 years would multiply prices more than fourfold.
This is why a 'modest' 2–3% rate deserves attention. It is nearly invisible year to year and still cuts money's value by more than half over a working lifetime.
The basket is an average. It reflects a statistically typical household, which no individual household is. A renter in a city and an outright homeowner in a small town experience very different inflation in the same year.
Rises are more memorable than falls. Groceries, restaurants and fuel are bought often and their prices are noticed constantly. Categories that got cheaper — consumer electronics, telecom plans, clothing — fade from memory. The index counts both.
Quality adjustment is applied. If a phone costs the same as ten years ago but does far more, statisticians record part of that as a price decline. The methodology is defensible, but it does not match a wallet that pays the same number.
Asset prices are excluded. House prices and share prices sit outside the index because they are investments, even though a first-time buyer feels them more than anything in the basket.
Nominal is the number printed at the time; real is what remains once price changes are removed. A salary going from $30,000 in 1990 to $70,000 in 2025 is 2.3 times more nominally, but prices rose 2.46 times, so in real terms it slightly declined.
Any statement about pay, pensions or budgets over time only means something next to the inflation of the same period. When wage growth trails price growth, real pay falls while the payslip number climbs.
Saving works the same way. A deposit paying 2% while prices rise 2.6% loses purchasing power every year, and tax on the interest widens the gap.
A quick estimate of the real return is the nominal rate minus inflation. The exact expression is (1 + nominal) ÷ (1 + inflation) − 1, but subtraction is close enough when both rates are small.
Reading historical figures. A wage or price quoted in an old article means little until it is restated in today's money. US prices rose about 8.3 times between 1970 and 2025.
Judging long-dated commitments. A fixed sum promised decades ahead quietly shrinks. Whether a contract or pension is index-linked matters more than its headline number.
Setting savings targets. A goal of $1,000,000 twenty years out is not today's million. At 2.5% inflation it is worth roughly $610,000 in current terms.
Comparing across generations. Converting a parent's first salary or first home price into today's money puts a number on how much of 'things were cheaper then' actually holds.
About $246 in 2025 by the US CPI. The index went from 130.658 in 1990 to 321.962 in 2025, a factor of 2.46. That works out to 2.61% average annual inflation.
Converted amount = amount × (index in the comparison year ÷ index in the starting year). For $100 from 1990 to 2025: 100 × (321.962 ÷ 130.658) ≈ $246. The cumulative rate is (ratio − 1) × 100 and the annual rate is (ratio^(1 ÷ years) − 1) × 100.
The CPI weights a fixed basket by average household spending, and your spending is not the average. If rent is a large share of your budget or you eat out often, your lived inflation runs above the index; if you spend more on categories that got cheaper, such as electronics and telecoms, it runs below.
No. The CPI covers goods and services that households consume. Buying a house or a share is investment rather than consumption, so those prices are excluded — though rent is included as a housing cost. That is why the index and public sentiment diverge most when asset prices surge.
Match the index to the currency of the amount: dollars with US CPI, won with Korea CPI. Applying one country's basket to another country's money gives a wrong answer, and this calculator does not convert between currencies.
US figures come from the monthly CPIAUCSL series published via FRED, reduced to annual averages from 1947 onward. Korean figures use the annual consumer price index compiled by the World Bank from 1960 onward. Both run through 2025; a year in progress is left out because its annual average is not settled yet.
What this tool bases its numbers on, and how far those numbers go.
Converted = amount × (end-year CPI ÷ start-year CPI) · cumulative rate = (ratio − 1) × 100 · annual rate = (ratio^(1 ÷ years) − 1) × 100, a geometric mean · buying power left = amount ÷ ratio$100 in 1990 → 2025: 100 × (321.962 ÷ 130.658) ≈ $246 · cumulative +146% · 2.61% a year · buying power left about $41