An inflation calculator answers one question: how much would X dollars from one year buy in another? Enter a starting amount, a starting year, an ending year, and a rate โ the calculator applies the compounding formula and shows you the real purchasing-power difference. If you want to skip straight to the numbers, use the Inflation Calculator โ and come back for the interpretation.
The May 2026 CPI report from the Bureau of Labor Statistics shows prices rising 4.2 percent over the past twelve months. That number sounds abstract until you run it through the calculator and see, for example, that $50,000 of purchasing power in 2021 now requires roughly $61,500. The tool makes the abstraction concrete.
What an inflation calculator actually measures
An inflation calculator does not predict future prices. It measures past or projected changes in purchasing power using one of two approaches:
Historical mode: You enter a dollar amount, a past year, and a target year. The calculator looks up the Consumer Price Index for each year and adjusts by the ratio `CPI_target / CPI_start`. This is the same methodology the BLS online CPI calculator uses.
Projection mode: You enter a dollar amount, a number of years, and an assumed annual rate. The calculator applies the compounding formula: `Future Price = Amount ร (1 + rate)^years`. This tells you what something that costs a given amount today would cost if inflation continues at the chosen rate.
Both modes answer the same underlying question. The difference is whether you are working with real historical data or a "what if" scenario.
The three inputs explained
Starting amount. The dollar figure you want to adjust. This can be a salary, a savings balance, a rent payment, a price tag โ any number denominated in dollars.
Years (or start year / end year). The time span over which inflation compounds. A 1-year gap at 4% looks manageable; a 20-year gap at 4% is not. Doubling time at 4% is about 17.5 years (use the Rule of 70: 70 รท 4 = 17.5 years). Use the Inflation Calculator โ to run any span without doing the arithmetic.
Inflation rate. The most consequential input โ see the section below on which rate to choose.
Step-by-step: a worked example
Suppose you want to know whether a $75,000 salary offered today is competitive with the $65,000 you made in 2020.
That means the $75,000 offer is actually a real pay cut of about 10% compared to your 2020 income. The nominal number went up; the real number went down. This is the single most useful thing an inflation calculator tells people during salary negotiations.
Three use cases worth running
1. Purchasing power over time
The historical application. $1.00 in January 2000 buys approximately $0.51 worth of goods in 2026 โ prices have essentially doubled since then, a cumulative increase of roughly 95 percent over 26 years (BLS historical CPI data). Use this when evaluating an old investment (did your 2005 home sale actually make money in real terms?), looking at historical contract terms, or understanding what a retirement account balance from a decade ago is truly worth today.
2. Salary and raise adequacy
Enter your salary from 3โ5 years ago, adjust to today, and compare to your current pay. Raises below the inflation rate mean you are getting poorer at work. In 2022โ2023, when CPI peaked at 9.1% (BLS, June 2022), employees who received 3% merit raises lost purchasing power at roughly 6% per year โ even though their paychecks grew. The calculator quantifies that gap clearly.
3. Retirement and long-term savings planning
Enter your current spending ($5,000/month is a common benchmark) and project it 20โ30 years forward. At the Fed's 2% long-term target, $5,000/month of today's expenses becomes about $7,430/month in 2046. At the current 4.2% rate, it becomes $11,388/month. The difference โ $3,958/month โ is why the inflation assumption you plug into your Retirement Calculator matters enormously. Running the inflation calculator alongside your retirement projections shows whether your assumed withdrawal rate will actually cover future costs.
What $10,000 of goods costs at three inflation rates
| Rate | After 5 yrs | After 10 yrs | After 20 yrs | After 30 yrs |
|---|---|---|---|---|
| 2% (Fed target) | $11,041 | $12,190 | $14,859 | $18,114 |
| 3% (30-yr historical avg) | $11,593 | $13,439 | $18,061 | $24,273 |
| 4.2% (May 2026 rate) | $12,284 | $15,090 | $22,770 | $34,358 |
*Starting amount: $10,000. Shows what the same goods and services would cost at each rate. Source: BLS CPI-U methodology.*
Which inflation rate should you enter?
This is the question that trips most people up. There is no single right answer โ pick a rate based on your planning horizon:
2.0% โ The Federal Reserve's stated long-run target (Federal Reserve FAQs). Use this for optimistic projections or when modeling what policymakers intend.
2.5โ3.0% โ The rough US average over the last 30 years (1996โ2026), which includes the 2021โ2023 spike and the stable 2010s (BLS CPI Historical Tables). Use this as a baseline for most retirement and long-term financial planning.
4.2% โ The May 2026 reading (BLS, June 2026). Use this for near-term projections when the current rate is relevant, or to stress-test your plans against continued elevated inflation.
For most people doing retirement planning, 3% is a reasonable middle-ground assumption. If you want to see the range of outcomes, run the calculator three times โ once at 2%, once at 3%, once at the current rate โ and decide where reality is most likely to land for your timeline.
Three things people misread in the output
Confusing real and nominal returns. If your savings account paid 0.5% in 2021 while CPI hit 7.0% (BLS), your real return was roughly -6.5% โ you lost purchasing power even though your balance grew. The inflation calculator does not do this math for you; subtract the inflation rate from your nominal yield, or use the Investment Return Calculator, which accepts an inflation input and shows the real-return figure directly.
Using headline CPI when a category rate is more relevant. The all-items CPI is a basket average. The BLS Medical Care Index has risen faster than the all-items basket โ approximately 3โ4% annually over recent years (BLS Medical Care CPI series). If you are projecting healthcare costs in retirement, plug a higher rate into the calculator for that portion of your budget โ the headline all-items CPI will underestimate your exposure.
Treating the output as a prediction. The calculator models a chosen rate compounded over a chosen period. Actual inflation will deviate from any fixed assumption โ the 2020s have already shown that CPI can move from 1.2% to 9.1% (BLS, June 2022) and back toward 3% within five years. Use the output to understand the order of magnitude of purchasing-power risk, not as a literal forecast of what bread costs in 2040.