Inflation Calculator: Value of Money Over Time

Inflation Calculator

An inflation calculator restates an amount of money from one year at another year's prices. It answers questions such as "what would $100 from 1990 buy in 2025?", and it reports how much prices changed in between.

What the calculator does

The calculator works from a consumer price index (CPI). A price index tracks the average price of a fixed basket of goods over time. The index number by itself has no unit. Only the ratio between two readings carries meaning. If the index was 100 one year and 125 another, prices are 25% higher, so an amount of money must be 25% larger to buy the same basket.

The tool has three modes:

1. Country price index. Pick a country and two calendar years. The tool looks both index readings up in a bundled table.
2. My own index values. Enter the two index readings yourself, plus the number of years between them.
3. Average annual rate. Enter one flat yearly rate and a number of years, then carry an amount forward or back in time.

Every mode returns three numbers: the equivalent amount, the cumulative price change over the whole period, and the annualized rate. Percentages are shown to two decimal places.

The inflation formula

For the two index modes, the whole calculation rests on one ratio:

ratio = CPI(to) ÷ CPI(from)

• equivalent amount = amount × ratio
• cumulative price change = ratio − 1
• annualized rate = ratio^(1 ÷ n) − 1, where n is the length of the period in years

Which reading is the "from" and which is the "to" is the only direction control the index modes need. The same formula answers both "what is a past amount worth now" and "what would today's amount have been worth then". When both years are the same, the period has zero length, so the calculator returns the amount unchanged with a zero rate rather than raising the ratio to the power of infinity.

The average-annual-rate mode compounds one rate instead of reading an index:

• growth = (1 + r)^n, where r is the rate divided by 100
• forward: equivalent amount = amount × growth
• backward: equivalent amount = amount ÷ growth

The cumulative change stays growth − 1 in both directions, because the price change belongs to the period and not to the direction of conversion.

This is the method the U.S. Bureau of Labor Statistics documents for its own CPI Inflation Calculator, which uses the average index for a calendar year. Reading an index ratio as a percent change is defined in the BLS CPI questions and answers page, under "How do I read or interpret an index?".

Example: $100 from 1990 at 2025 prices

The shipped U.S. table gives an annual average CPI-U of 130.7 for 1990 and 321.943 for 2025.

• ratio = 321.943 ÷ 130.7 = 2.4632
• equivalent amount = $100 × 2.4632 = $246.32
• cumulative price change = 2.4632 − 1 = +146.32%
• annualized rate = 2.4632^(1 ÷ 35) − 1 = 2.61% per year

So $100 in 1990 had the buying power of about $246 in 2025, and prices rose 146.32% across those 35 years.

The same period read backwards

Swapping the two years inverts the ratio. With 2025 as the "from" year and 1990 as the "to" year, $100 becomes $40.60, a change of −59.40%, or −2.54% per year. Both readings describe the same price history. A rise of 146.32% in one direction is a fall of 59.40% in the other, because the two are reciprocals rather than opposites.

Prices can also fall

Spain's index fell from 94.023 in 2013 to 93.412 in 2015. Entering €100 for those years returns €99.35, a cumulative change of −0.65%, or −0.33% per year. A sustained fall in the general price level is called deflation.

Example: a flat 3% for ten years

In average-annual-rate mode, $100 at 3% a year for 10 years gives growth of 1.03^10 = 1.3439.

• forward: $100 × 1.3439 = $134.39
• backward: $100 ÷ 1.3439 = $74.41
• cumulative change either way: +34.39%

A single flat rate is a rough model. It will not match a country's real year-by-year path.

The bundled price index tables

Four national series ship with the tool. Each one names its issuing agency, its base period, how the annual figure was obtained, the years it covers, and the date it was retrieved, both on the page and in the source code.

All four tables were retrieved on 2026-09-05, and that date is shown next to the series on the page. Statistical agencies revise and rebase these series, so figures published after that date can differ from the ones bundled here. Anyone who has newer or different official numbers can override the table: the "My own index values" mode uses only the two readings entered, and no bundled table is applied.

The U.S. and German figures are each agency's own published annual average. IBGE and INE publish their indices monthly and not as an annual figure, so those two tables use the mean of the twelve published monthly readings for the year, which is the same definition BLS and Destatis apply to their own annual averages.

Brazil's table starts in 1995 on purpose. The real replaced the cruzeiro real in July 1994 at 2,750 to 1, so an amount from 1994 or earlier is written in a different currency, and rescaling it by the index alone would give a figure in no currency at all.

Limits

• No currency is converted. An amount entered in euros comes back in euros, rescaled by that same currency area's own price level.
• The tables are annual, not monthly. Country mode accepts whole calendar years only.
• A year outside a table's range is refused, and the message names the range the series covers.
• The two custom modes accept periods up to 1,000 years. Longer spans are refused, because the exponent stops producing a meaningful figure.
• An index reading of zero or less, an amount of zero or less, and a rate at or below −100% are all refused. No price level can shrink to zero or turn negative.
• This is a general inflation calculator. It is not the Banco Central do Brasil's Calculadora do Cidadão, and it does not apply contract correction indices such as IGP-M or INPC.

Frequently asked questions

What does "$100 in 1990 is worth $246.32 in 2025" actually mean? It means an average basket of goods that cost $100 in 1990 cost about $246.32 in 2025. It is a statement about average prices, not about any single product. Rent, food and electronics all move at different speeds.

Why is the annualized rate so much smaller than the total change? The cumulative change covers the whole period at once. The annualized rate is the steady yearly rate that would compound to that same total. Prices rising 146.32% over 35 years works out to 2.61% a year, because each year's rise is applied on top of the last.

Does the calculator convert between currencies? No. The answer is always in the same currency as the amount entered. The tool only rescales the amount by a price index or a rate.

My country is not in the list. Can I still use it? Yes. Take the two index readings from that country's own statistical agency and enter them in the "My own index values" mode, along with the number of years between them. The same ratio formula is applied to the entered figures.

Why might these results differ from an official calculator? Two common reasons. Official tools often work from monthly index values, while these tables are annual. And agencies revise and rebase their series, so a table retrieved on 2026-09-05 can differ from one published later.

Can the result be negative? The equivalent amount cannot, because the amount and both index readings must be greater than zero. The cumulative change and the annual rate can be negative, which means prices fell over the period.

References

1. "CPI Inflation Calculator." U.S. Bureau of Labor Statistics, https://www.bls.gov/data/inflation_calculator.htm.
2. "Consumer Price Index: Questions and Answers." U.S. Bureau of Labor Statistics, https://www.bls.gov/cpi/questions-and-answers.htm.
3. "Consumer Price Index for All Urban Consumers (CPI-U), series CUUR0000SA0." U.S. Bureau of Labor Statistics, https://www.bls.gov/cpi/.
4. "Verbraucherpreisindex für Deutschland." Statistisches Bundesamt (Destatis), https://www.destatis.de/EN/Themes/Economy/Prices/Consumer-Price-Index/_node.html.
5. "Índice Nacional de Preços ao Consumidor Amplo (IPCA)." Instituto Brasileiro de Geografia e Estatística (IBGE), https://www.ibge.gov.br/en/statistics/economic/prices-and-costs/17136-national-index-of-consumer-prices.html.
6. "Índice de Precios de Consumo (IPC)." Instituto Nacional de Estadística (INE), https://www.ine.es/dyngs/INEbase/en/operacion.htm?c=Estadistica_C&cid=1254736176802&menu=ultiDatos&idp=1254735976607.