Inflation Calculator
Convert an amount between any two months since 1913 using published U.S. CPI data, or project it forward and backward at a flat rate.
How to use these calculators
There are three tools on this page, each answering a different question. All three take an amount in U.S. dollars and leave your figures untouched when you use another.
- Inflation Calculator with U.S. CPI Data — enter an amount, then pick the period it belongs to and the period to value it in. Either end can be a single month or a whole year's average. This one reports what really happened, using published index values rather than an assumed rate.
- Forward Flat Rate — enter an amount, a rate you expect, and a number of years, to project a price into the future.
- Backward Flat Rate — the same rate read the other way, to find what an amount would have been worth that many years ago.
Where the CPI data comes from
The CPI calculator uses the Consumer Price Index for All Urban Consumers (CPI-U), U.S. city average, all items, not seasonally adjusted — the Bureau of Labor Statistics series CUUR0000SA0, on its 1982-84 = 100 base. It covers every month from 1913 to the most recent release. An annual average is the mean of that year's twelve monthly values, which is how the Bureau publishes it, so the 2016 average shown here is 240.007 exactly as BLS prints it.
One month is missing on purpose. Prices were never collected in October 2025 because of that year's lapse in appropriations, so no index exists for it and 2025 has no annual average at all. That month is left out rather than filled in from its neighbours — an interpolated figure would look like data while being a guess, and the whole value of an index is that someone actually went and measured it.
How the CPI comparison works
Converting an amount between two periods is one division. The index in each period stands for the price of the same basket of goods, so the ratio between them is how much more (or less) money it takes to buy the same things:
Value = amount × (CPI at the end ÷ CPI at the start)
Take the ten years to July 2026. The CPI averaged 240.007 across 2016 and stood at 333.918 in July 2026, so $100 of 2016 buying power is 100 × 333.918 ÷ 240.007 = $139.13. Prices rose 39.13% in total. Spread across the decade that is 3.36% a year — the compound rate, not 39.13 ÷ 10, because each year's inflation applies to the prices the previous year left behind.
The flat-rate formula
The other two calculators assume a constant rate rather than looking anything up, which is what you need to project past the last release or to test a scenario. Inflation compounds, so the rate is applied year on year:
Forward = amount × (1 + r)t
Backward = amount ÷ (1 + r)t
- amount — the sum you entered
- r — the annual inflation rate as a decimal (3% = 0.03)
- t — the number of years
The two are mirror images. At a steady 3%, something costing $100 today costs about $134.39 in ten years, and $100 today had the buying power of about $74.41 ten years ago. Multiply those two results together and you get back to $10,000 — 100 × 100 — which is the arithmetic check that they really are the same formula read in opposite directions.
The rule of 72
For a quick mental estimate, divide 72 by the inflation rate to see how many years it takes prices to double. At 3%, that is 72 ÷ 3 = about 24 years; at 6% it halves to 12. The same shortcut works for investment growth — which is exactly why your returns need to clear the inflation rate to make real progress.
Protecting your buying power
Money that does not grow at least as fast as inflation quietly loses value. At 3%, cash left idle loses roughly a quarter of its buying power in a decade, which is why savings and investments generally need to earn a return above the inflation rate to make real progress. Model that growth with the investment calculator and the compound interest calculator.
Limitations to keep in mind
- A general index, not your basket. The CPI tracks a broad basket of goods; your personal inflation rate depends on what you actually buy. Housing, food and energy rarely move together.
- The index gets revised. Recent months can be revised after first publication, and the basket itself is periodically reweighted.
- Constant-rate assumption. The two flat-rate tools apply one steady rate; real inflation varies year to year.
- Before taxes and returns. These measure price change only, not the growth of any money you invest to keep pace.
This is general educational information, not financial advice.
Frequently asked questions
What is inflation?
Inflation is a general, sustained rise in prices across an economy, which means each unit of money buys a little less over time. It is usually expressed as an annual percentage — 3% inflation means a basket of goods that cost $100 last year costs about $103 this year.
Where does the CPI data come from?
The first calculator uses the U.S. Consumer Price Index for All Urban Consumers (CPI-U), U.S. city average, all items, not seasonally adjusted — the Bureau of Labor Statistics series CUUR0000SA0 on its 1982-84 = 100 base. It runs monthly from 1913 to the most recent release, and an annual average is the mean of that year's twelve monthly index values.
Why is there no October 2025 figure?
Prices were never collected that month. The 2025 lapse in appropriations stopped data collection, so the Bureau published no October 2025 index and, because a year needs all twelve months, no 2025 annual average either. The month is left genuinely missing here rather than filled in by averaging its neighbours, which would invent a number that was never measured.
How is the average annual inflation rate worked out?
It is the compound annual rate that turns the starting index into the ending one, not the simple average of the yearly changes. Over ten years a total rise of 39.13% works out to 3.36% a year, because each year compounds on the last. An annual average is placed at the middle of its year, July, when the length of a span is measured.
What is the difference between the CPI and the flat-rate calculators?
The CPI calculator reports what actually happened: it looks up two published index values and divides. The flat-rate calculators assume a steady rate you choose, which is what you want for projecting into the future or for a quick estimate over a period the index does not cover.
What causes inflation?
Broadly three forces: demand-pull (more spending chasing the same goods), cost-push (rising costs of labour, energy or materials pushing prices up), and monetary expansion (the money supply growing faster than the economy). Most real-world inflation is a mix of all three.
What inflation rate should I use for the flat-rate calculators?
Long-run U.S. inflation has averaged around 2–3% a year, and the Federal Reserve targets about 2%. Individual years swing well above and below that. Treat any single rate as a scenario rather than a forecast, and try two or three to see how sensitive a long horizon is to the choice.
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About this calculator
Method reviewed for accuracy on July 23, 2026
Built on transparent, unit-tested formulas that run entirely in your browser — see how we build our calculators.
References: Inflation table
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