Inflation Calculator

Compare purchasing power between completed U.S. CPI-U years from 1913 through 2025, or model a future amount with a constant annual inflation or deflation rate. See equivalent value, cumulative price change, purchasing power retained, a year-by-year chart, and the full schedule.

Calculation

Amount

Starting year

Ending year

How to Use the Inflation Calculator

Choose Historical CPI to compare U.S. dollar purchasing power between two completed years. Enter an amount, choose the starting and ending years, and use the swap control when you want to run the comparison backward.

Choose Future scenario when you want to test a constant inflation or deflation assumption. Enter the starting amount, starting year, target year, and annual rate.

The main result shows the equivalent amount. Supporting figures show the cumulative price-level change, the compound annualized rate, the purchasing power retained by the unchanged nominal amount, and the difference between the starting and equivalent amounts.

Open Year-by-year details for the chart, the CPI values used in historical mode, the complete yearly schedule, printing, and CSV export.

**Choose the right calculation mode**
Mode	Data or assumption	What it answers
Historical CPI	U.S. CPI-U annual averages, 1913–2025	What amount in one completed year had roughly the same broad U.S. consumer purchasing power in another completed year?
Future scenario	One constant annual rate entered by you	What would an amount become if that inflation or deflation rate continued for the full period?

What Is $1 From One Year Worth in Another Year?

Historical mode answers that question by comparing two annual Consumer Price Index values. The starting amount is multiplied by the ending-year CPI divided by the starting-year CPI.

For example, annual CPI-U was 82.4 in 1980 and 321.943 in 2025. The ratio is about 3.9071, so $1,000 in 1980 corresponds to about $3,907.08 in 2025 under this broad consumer-price comparison.

This is a purchasing-power equivalence, not a claim that every product, salary, house, investment, or household expense rose by the same multiple.

Equivalent Amount and Purchasing Power Are Two Views of the Same Ratio

Equivalent amount asks how much money would be needed in the ending year to match the starting amount's modeled purchasing power.

Purchasing power retained asks the reverse question: if the nominal amount never changes, how much of its original purchasing power remains?

With the 1980-to-2025 example, the modeled price level rises about 290.71%. The unchanged $1,000 retains about 25.59% of its 1980 purchasing power, or roughly $255.95 in 1980 dollars.

**What each result means**
Result	Meaning
Equivalent amount	The ending-year amount that matches the starting amount under the selected CPI ratio or constant-rate scenario
Price-level change	The cumulative change in the modeled price level across the full period
Average annual rate	The compound yearly rate connecting the starting and ending price levels
Purchasing power retained	The percentage of starting-year purchasing power represented by keeping the nominal amount unchanged
Amount difference	Equivalent ending amount minus the starting amount

Why a 100% Price Increase Means a 50% Purchasing-Power Loss

Inflation and purchasing-power loss are reciprocal effects, not equal percentages with opposite signs.

If prices double, the equivalent amount rises from $100 to $200, which is a 100% increase. But an unchanged $100 now buys only half as much, so 50% of the original purchasing power remains.

That is why cumulative inflation of 100% does not mean purchasing power fell 100%. A 100% purchasing-power loss would mean the money buys nothing at all.

Annual-Average CPI Is Not the Same as December-to-December Inflation

This calculator uses annual-average CPI-U. An annual average is based on the year's 12 monthly CPI index values and represents an average price level for that calendar year.

December-to-December inflation compares two particular monthly indexes instead. Because the reference periods are different, the two percentages can differ even when they refer to the same pair of calendar years.

Using completed annual averages keeps the historical series internally consistent. The calculator therefore does not mix partial current-year CPI with the completed annual series.

**Selected annual U.S. CPI-U values**All items, U.S. city average, 1982–84 = 100. The calculator uses the complete annual series, not just these selected rows.
Year	Annual CPI-U	Context
1913	9.9	First year in this calculator's annual series
1920	20	Selected historical benchmark
1933	12.9	Selected deflation-era benchmark
1950	24.1	Selected historical benchmark
1980	82.4	Selected historical benchmark
2000	172.2	Selected historical benchmark
2020	258.811	Selected historical benchmark
2025	321.943	Latest completed annual average in this calculator

How Reverse Historical Comparisons Work

The CPI ratio works in either direction. A forward comparison divides a later year's CPI by an earlier year's CPI. A reverse comparison divides the earlier CPI by the later CPI.

Using the same 1980 and 2025 values, $1,000 in 2025 corresponds to about $255.95 in 1980 purchasing power.

Reverse calculations do not undo history or imply that prices literally moved backward. They simply express an amount in the purchasing-power terms of the other selected year.

Historical Deflation Works the Same Way

CPI does not rise every year. When the ending annual CPI is below the starting annual CPI, the calculator reports a lower equivalent amount and a negative price-level change.

For example, annual CPI-U fell from 17.2 in 1929 to 12.9 in 1933. Under that broad index comparison, an unchanged nominal amount gained purchasing power across the interval.

The same ratio method handles inflation, deflation, and unchanged price levels without changing formulas.

How Future Inflation Compounds

Future mode does not use CPI data after the latest completed annual average. Instead, it compounds the rate you enter for the number of years between the starting and target dates.

At a constant 2.5% annual rate, $1,000 becomes about $1,638.62 after 20 years. The modeled price level rises about 63.86%, while the unchanged $1,000 retains about 61.03% of its starting purchasing power.

Compounding matters because each year's increase applies to the previous year's already-adjusted amount rather than repeatedly adding the same flat dollar amount.

A Future Inflation Rate Is a Scenario, Not a Forecast

Real inflation does not stay fixed. It can accelerate, slow, turn negative, or vary substantially from one year to the next.

A constant-rate projection is useful for answering conditional questions such as what a $1,000 expense would become if inflation averaged 2%, 3%, or 5% over a chosen period.

For planning, compare several plausible assumptions instead of treating one entered rate as a prediction.

Why Your Personal Inflation Can Differ from CPI-U

CPI-U is a broad statistical measure of price change for urban consumers. It is not a personalized basket built from one household's spending.

A household that spends unusually large shares on rent, medical care, education, transport, food, or another category can experience a different price path from the headline all-items index.

Location, consumption patterns, product substitutions, quality changes, taxes, and individual purchasing decisions can also make lived inflation differ from the broad average.

CPI Purchasing Power Is Not a Personal Cost-of-Living Calculator

CPI is useful for comparing broad consumer purchasing power over time, but it does not tell you what it costs a specific person to maintain the same lifestyle in two places or two years.

A personal cost-of-living comparison would need household-specific spending, location, housing, taxes, healthcare, transport, and other information that this calculator does not collect.

Likewise, CPI alone cannot determine whether a wage kept pace with someone's actual expenses or whether an investment produced a positive real return.

**Important inflation distinctions**
Concept	What it means here	Not the same as
Annual-average CPI	The average of the 12 monthly index values for a calendar year	A specific month's CPI or December-to-December inflation
CPI purchasing power	A broad comparison based on average consumer-price change	One household's exact cost of living
Future inflation scenario	Compound growth or decline at one constant rate	A forecast of future inflation
Inflation adjustment	A mathematical change based on a chosen price index or rate	Investment return, wage growth, exchange-rate conversion, or asset appreciation

What This Inflation Calculator Does Not Model

Historical mode does not use monthly CPI, partial-year estimates, another country's price index, regional CPI, category-specific CPI, or a personal spending basket.

Future mode does not forecast inflation, assign probabilities, or vary the rate automatically from year to year.

The calculator also does not convert currencies, calculate investment returns, value assets, decide wage adjustments, or determine which index should be used in a contract, pension, lease, court order, or government program.

Inflation and Purchasing-Power Formulas

Historical mode uses annual CPI ratios. Future mode applies compound growth or decline at the constant annual rate entered.

Historical equivalent amount

V_{2} = V_{1} \frac{C P I _{2}}{C P I _{1}}

Historical cumulative price change

Δ P = (\frac{C P I _{2}}{C P I _{1}} - 1) \times 100

Purchasing power retained

P P = \frac{C P I _{1}}{C P I _{2}} \times 100

Historical annualized rate

r_{a} = [(\frac{C P I _{2}}{C P I _{1}})^{1/ n} - 1] \times 100

Future equivalent amount

V_{f} = V_{0} (1 + r)^{n}

Future purchasing power of an unchanged amount

V_{real} = \frac{V _{0}}{( 1 + r ) ^{n}}

$V_{1}$: Amount in the starting historical year
$V_{2}$: Equivalent amount in the ending historical year
$C P I_{1}$: Starting-year annual CPI-U
$C P I_{2}$: Ending-year annual CPI-U
$n$: Number of elapsed years
$r_{a}$: Historical compound annualized price-change rate
$V_{0}$: Starting amount in a future scenario
$r$: Future annual inflation or deflation rate written as a decimal
$P P$: Percentage of starting purchasing power retained by the unchanged nominal amount

Examples

Convert 1980 dollars to 2025 dollars

$1,000 in 1980; ending year 2025.

Using annual CPI-U values of 82.4 and 321.943, the equivalent amount is about $3,907.08.

The unchanged $1,000 retains about 25.59% of its 1980 purchasing power, equivalent to roughly $255.95 in 1980 dollars.

Run the same comparison backward

$1,000 in 2025; ending year 1980.

The equivalent amount is about $255.95 in 1980 purchasing power.

The reverse calculation uses the reciprocal CPI ratio.

Compare a historical deflation period

$100 in 1929; ending year 1933.

The equivalent amount falls because annual CPI-U declined from 17.2 to 12.9.

The unchanged nominal $100 therefore has greater purchasing power in the ending year under the broad CPI comparison.

Project an expense for 20 years

$1,000 in 2026; target year 2046; annual inflation 2.5%.

The constant-rate scenario produces an equivalent amount of about $1,638.62.

The modeled price level rises about 63.86%. The unchanged $1,000 retains about 61.03% of its starting purchasing power.

Model future deflation

$1,000 over 10 years at -1% per year.

The equivalent target amount falls to about $904.38.

A negative rate above -100% models a declining price level rather than an inflation forecast.

Frequently Asked Questions

What data does Historical CPI mode use?

It uses U.S. CPI-U all-items annual averages from 1913 through 2025.

Why does historical mode use U.S. dollars only?

The historical dataset measures U.S. consumer prices. Changing the currency symbol would not turn that series into another country's inflation history.

Why does the calculator stop at 2025 for historical CPI?

Historical mode uses completed annual averages. The 2025 annual CPI-U average is the latest completed annual value included in this version of the calculator.

Can I compare years in reverse?

Yes. The calculator uses the ending-year CPI divided by the starting-year CPI, so the same formula works in either chronological direction.

Why is purchasing-power loss different from cumulative inflation?

They are reciprocal effects. If the price level doubles, the required equivalent amount rises 100%, while an unchanged nominal amount retains 50% of its original purchasing power.

What does average annual inflation mean here?

For historical comparisons it is the constant compound yearly rate that connects the selected starting and ending annual CPI values. It is not the arithmetic average of yearly inflation percentages.

Can historical inflation be negative?

Yes. If the ending annual CPI is lower than the starting annual CPI, the calculator reports deflation and a lower equivalent amount.

Why can another inflation calculator show a different result?

Another calculator may use monthly CPI, December-to-December indexes, a partial current-year estimate, a different CPI series, another country, or different rounding.

Is annual-average CPI the same as December inflation?

No. An annual average summarizes the 12 monthly CPI index values for the year. December-to-December inflation compares two specific monthly indexes.

Does Future scenario mode predict inflation?

No. It compounds the rate you enter for the selected number of years. The result answers what would happen under that assumption, not what inflation will actually be.

Can I use another currency in Future scenario mode?

Yes for formatting a generic constant-rate scenario. The calculator does not convert exchange rates or supply historical inflation data for that currency's country.

Does CPI measure my personal cost of living?

Not exactly. CPI-U is a broad urban consumer price index. Your spending mix, location, housing, healthcare, transport, taxes, and other costs can produce a different personal experience.

Can I use this result to adjust a salary, pension, lease, or contract?

Only if the relevant rule explicitly uses the same index, reference period, and calculation method. Many agreements and programs specify their own index, month, cap, floor, or rounding procedure.

Can I export the year-by-year calculation?

Yes. The detailed result includes a paginated table, while CSV export contains the complete modeled yearly schedule.