The formula
Worked examples
How to calculate inflation calculator
This uses the actual published CPI-U index for each year rather than compounding an assumed flat inflation rate, which is what makes it match the "what would $X from 1990 be worth today" figures quoted elsewhere. The index itself is just a number the BLS anchors to 100 for the 1982-1984 average; everything else is read relative to that.
The ratio between the two years' index values is the whole calculation. $100 in 2000 (index 172.2) against 2025 (index 321.943) gives a ratio of 1.87, so $100 then buys the same as roughly $187 does now — prices, on average, nearly doubled over that 25-year span.
What to enter:
- Amount ($)
- From year
- To year
Everything recalculates as you type, and the numbers in the address bar update with it, so a link to this page carries your figures with it.
Some of the fields above will accept figures that seem unusual for your own situation, and that is deliberate: the formula behind inflation calculator works the same way regardless of scale, so the calculator does not stop you testing a hypothetical scenario a long way from your actual numbers — often the fastest way to see which input the result is most sensitive to.
Why inflation calculator matters
The formula behind inflation calculator is standard and has not changed in decades; what changes is the situation it gets applied to. Two households can run the identical calculation and land on very different conclusions once their own numbers — income, rate, term, balance — are dropped in, which is why a generic textbook example is less useful than a calculator you can adjust to match your own circumstances.
Beyond a one-off check, the same calculation is worth revisiting whenever the underlying numbers change — a new interest rate, a change in income, a different term. Because the figures live in the page's own web address, coming back to update just one field and compare the new result against the old one takes seconds rather than starting again from a blank page.
The reason a page like this exists at all, rather than leaving the calculation to a spreadsheet or a textbook appendix, is that the formula behind inflation calculator is fiddly enough to get wrong by hand but not complicated enough to need specialist software. That middle ground — real enough maths to matter, simple enough to check instantly — is exactly what a dedicated calculator is for, and it is why the same figure recalculated here should match a careful manual calculation almost exactly.
A calculator like this one is often bookmarked and returned to repeatedly over months rather than used once, particularly for anything tied to an ongoing plan such as a mortgage, a savings goal or an investment being tracked. Because the figures live in the web address rather than only in memory, coming back to the same page with updated numbers is quicker than starting from a blank spreadsheet each time.
Worked example
Take the figures the calculator starts with:
- Amount: 100 $
- From year: 2,000
- To year: 2,025
That gives:
- Equivalent amount: 186.96 $
- Cumulative inflation: 86.96 %
These figures are only the calculator's own starting values, included so the working is visible rather than hidden inside the tool above. Replace them with your own numbers and the same arithmetic applies — nothing about the method changes, only the inputs feeding it.
Reading the result
CPI-U tracks a broad basket of goods and services for the average urban household — it is not personal to any one budget. Someone whose spending leans heavily on categories that ran hotter than average (housing and medical care, in most recent decades) has experienced worse-than-average inflation; someone leaning on categories like electronics has experienced less.
Where this goes wrong. Assuming a constant year-on-year rate gives a different, usually less accurate, answer than reading the real index. Inflation was close to zero in some years (2009, 2015) and above 8% in others (2022) — a single average rate compounded smoothly over the same period misses that unevenness and can be off by a meaningful margin over a long span.
A useful check on any unfamiliar result is to compare it against a rough mental estimate first — round the inputs to convenient numbers and see whether the calculator's answer lands in roughly the same territory. A wildly different figure usually means one of the fields was entered in the wrong unit, most often a percentage typed as a whole number where a decimal was expected, or the reverse.
The Consumer Price Index for All Urban Consumers, the US Bureau of Labor Statistics' main inflation measure, based on a monthly survey of prices for a fixed basket of goods and services — housing, food, transport, medical care and more — covering roughly 93% of the US population.
Because more dollars are chasing largely the same real basket of goods over time, a mix of rising demand, rising costs of production, and central banks deliberately targeting mild ongoing inflation (typically around 2% a year) rather than flat prices, which carries its own economic risks.
It returns equivalent amount. With 100 $ amount, that comes to 186.96 $. Change any field and the figure moves with it.
Whenever one of the underlying figures changes — a new interest rate, a different balance, an updated term — since the result only reflects what is currently in the fields. There is no need to keep a separate record of past results; the web address for a filled-in version already carries the figures used to produce it.
Not unless a tax rate or a fee is explicitly one of the inputs above. Where it is not, the figure shown is a gross calculation, and any tax due depends on your personal circumstances and current tax rules, which are worth checking separately.
The arithmetic itself is exact — the calculator applies the formula shown above precisely, with no rounding until the final figure is displayed. The uncertainty, where it exists, is entirely in the inputs: an estimated rate or an approximate balance carries that same approximation through to the result.