# About ## Who runs this site I'm Kyle, and I run inflationcalculator.app by myself. It isn't a company, and I'm not a financial advisor, economist, or accountant. I'm someone in the United States who kept looking up what old prices are worth today and how different investments have held up, often enough that the tools I was using started to bother me. They worked, but they were cluttered and dull, and I didn't enjoy going back to them. I wanted a clean reference I would actually use, so I built one. ## What's here - The [Inflation Calculator](https://inflationcalculator.app/inflation) converts a dollar amount from any year between 1913 and 2026 into the dollars of any other year in that range. - The [Investment Calculator](https://inflationcalculator.app/investment) shows what a single sum put into the S&P 500, gold, US home prices, US bonds, or Bitcoin in a given year would be worth now, starting as early as 1990 (2010 for Bitcoin). - 113 year pages, from [/inflation/1913](https://inflationcalculator.app/inflation/1913) to [/inflation/2025](https://inflationcalculator.app/inflation/2025), each answering what $100 from that year is worth today, with that year's inflation rate and a table of common amounts. - 8 [guides](https://inflationcalculator.app/learn) on the CPI, the history of US inflation, and long-run investment returns. Everything is free and needs no account. The calculators run in your browser. ## Where the numbers come from Inflation figures use the Consumer Price Index for All Urban Consumers (CPI-U), US city average, all items, published by the US Bureau of Labor Statistics (series CUUR0000SA0, not seasonally adjusted, 1982–84 = 100). The site uses the annual average for each year, at the precision BLS publishes. 2026 isn't over, so its figure is the average of the months BLS has released so far (January–September), and it moves a little as each new month comes in. To convert an amount, the calculator multiplies it by the ratio of the two years' index values: amount × CPI(target year) ÷ CPI(starting year). The 1990 average is 130.7 and the 2026 average so far is 332.243, so $100 in 1990 is $100 × 332.243 ÷ 130.7 = $254.20 in 2026 dollars. Because these are annual averages, a result compares typical prices across a whole year, not on a particular day. The Investment Calculator uses one value per asset per year: - **S&P 500:** the index's year-end closing level. This is the price index, so dividends are not included. - **Gold:** the annual average of the LBMA gold price, in US dollars per troy ounce. - **US real estate:** the S&P Cotality Case-Shiller U.S. National Home Price Index (FRED series CSUSHPINSA, January 2000 = 100), December value. Price only: no rent, mortgage, or upkeep. - **US bonds:** the Bloomberg U.S. Aggregate Bond Index total return (interest reinvested) at each year-end, chained to 1990 = 100. The current year uses the year-to-date total return of the iShares Core US Aggregate Bond ETF (AGG). - **Bitcoin:** the year-end price in US dollars. The current-year value for each asset is its latest reading as of September 25, 2026. A sum grows by the ratio of the two values: amount × value(now) ÷ value(start year), and the annualized figure is the compound annual growth rate over the same span. Investment results are nominal: not adjusted for inflation, and before fees and taxes. Past returns don't predict future ones. The CPI updates itself: a scheduled job checks the BLS data every day and, within a day of each monthly release, recalculates the current-year average and republishes the site. Asset prices are updated by hand from the sources above, less often; the current readings are as of September 25, 2026. The year pages, the API, and most current-year figures in the guides are computed from the same tables, so they change together. ## How this site is made I build the site with the help of AI tools. The guides and most of the explanatory text on the calculator and year pages were drafted with an AI model at my direction and published by me. I'm responsible for everything here, including the parts an AI drafted. The numbers do not come from AI. Every figure in the calculators, on the year pages, and in the API is computed by the site's code from the public data described above, the same way every time. Each guide shows on its byline whether and when I have reviewed and fact-checked it. If you find a mistake, email me with the page and the figure. I check it against the original source, correct the page, and change its "Updated" date. ## Contact Email [contact@inflationcalculator.app](mailto:contact@inflationcalculator.app), or see the [contact page](https://inflationcalculator.app/contact) for what to include. For developers and AI agents: the same figures are available from a free JSON API at [/api](https://inflationcalculator.app/api) (no key needed), and [/llms.txt](https://inflationcalculator.app/llms.txt) describes the site for language models.