CPI Inflation Calculator
What a US dollar from any month since 1913 is worth today, and how much inflation took from S&P 500 returns.
$1,000 in January 2000 has the buying power of $1,996 in September 2026, a 99.6% rise in US consumer prices (CPI-U).
$10,000 in the S&P 500 at the start of 2000 grew to $73,856 by the end of 2025, but only $38,358 in 2000 dollars once inflation is removed (8.0% a year nominal, 5.3% a year real).
Data through September 2026, read on 2026-10-27. Change the months and years below.
What is a dollar amount worth in another month?
Uses the monthly CPI-U index. Your numbers stay in your browser.
$1,000.00 in January 2000 has the buying power of $1,996.09 in September 2026.
- Cumulative change
- 99.61%
- Per year
- 2.63%
- CPI-U January 2000
- 168.800
- CPI-U September 2026
- 336.940
How much of the S&P 500 return did inflation take?
Calendar years, total return with dividends reinvested, from the start of the first year to the end of the last.
$10,000 became $73,856 by the end of 2025, worth $38,358 in 2000 dollars.
- Nominal per year
- 7.99%
- Inflation per year
- 2.55%
- Real per year
- 5.31%
- Gain taken by inflation
- 56%
How it is calculated
Dollar converter. Your amount is multiplied by the CPI-U index of the later month and divided by the index of the earlier month. Cumulative inflation is that ratio minus 1, and the yearly rate is the ratio raised to the power 1 divided by the years between the two months, minus 1. This is the standard method for CPI conversions, not a formula quoted from BLS.
S&P 500 section. Each year's total return is divided by one plus that year's inflation, and the results are multiplied together. The yearly rates are the geometric mean of those years. The "gain taken by inflation" is 1 minus the real gain divided by the nominal gain.
Educational tool, not personal financial advice. Past inflation and returns do not predict future ones.
Sources
- U.S. Bureau of Labor Statistics, CPI-U series CUUR0000SA0 (U.S. city average, all items, not seasonally adjusted, 1982-84=100): "All items in U.S. city average, all urban consumers, not seasonally adjusted". Read on 2026-10-27.
- U.S. Bureau of Labor Statistics, CPI Inflation Calculator: "Calculations using October 2025 data will not be calculated.". Read on 2026-10-27.
- U.S. Bureau of Labor Statistics, CPI Questions and Answers (percent change example): "18.0/225.000 x 100 = 8.0". Read on 2026-10-27.
- Aswath Damodaran, NYU Stern, Historical Returns on Stocks, Bonds and Bills (S&P 500 annual total returns, via our market-history file). Read on 2026-10-27.
Inflation calculator FAQ
How do you calculate inflation between two dates?
Divide the CPI index of the later month by the index of the earlier month and multiply your amount by the result. For example, the CPI-U index was 315.605 in December 2024 and 324.054 in December 2025, so prices rose 2.68% and $100 became $102.68.
How much is $1 from January 1913 worth today?
Using the latest published month (September 2026), $1 in January 1913 has the buying power of $34.38. That is a 3,338% cumulative rise, about 3.2% a year.
Does the S&P 500 beat inflation?
Over 2000-2025 it did: 8.0% a year nominal against 2.6% a year of inflation leaves 5.3% a year real. Inflation took 56% of the nominal gain. Past years do not predict future ones, and individual years can be negative in real terms.
Which price index does this calculator use?
The CPI for All Urban Consumers (CPI-U), U.S. city average, all items, not seasonally adjusted, series CUUR0000SA0. It is the same series the BLS inflation calculator uses.
Why is there no result for October 2025?
BLS published no CPI value for October 2025, and its own calculator refuses that month. We do the same instead of guessing a number. Pick September or November 2025 instead.
Why does the S&P 500 section use calendar years?
Our S&P 500 history is annual total returns with dividends reinvested, 1928 to 2025. Inflation for those years is measured December to December with the same BLS CPI-U series the dollar converter uses.