A rough guide to how economists describe different inflation rates, with your computed rate marked. These labels are conventions, not official thresholds, and the right reading depends on context — a central bank target near 2% is typical for advanced economies, but tolerances differ across countries and eras.
Range
How it is usually described
Below 0%
Deflation — the price level is actually falling, which can deepen debt burdens and stall spending.
0% – 1%
Very low inflation, close to flat; sometimes a sign of weak demand or a sluggish economy.
1% – 3%
Low and stable — the comfort zone many central banks aim for, often centred on a 2% target.
3% – 6%
Moderate inflation; noticeable erosion of purchasing power that often draws a policy response.
◀ your rate (4.00%)
Above 6%
High inflation — prices rising fast enough to disrupt planning, contracts, and saving.
Calculated in your browser — the numbers you enter are never sent to our servers.
Inflation is the percentage change in the index, not the change in its points: (260 − 250) / 250 is 4%. Index levels are arbitrary — they are set to 100 in whatever base year the statistics office chose — so only changes carry meaning, and only changes expressed relative to the starting level.
This is why the same 10-point move means different things at different levels. From 100 to 110 is 10% inflation; from 250 to 260 is 4%; from 400 to 410 is 2.5%. Reporting index point changes as though they were rates is a common error in secondary coverage and always overstates inflation at higher index levels.
Three years at 4% is 12.49%, not 12%
Each year’s inflation applies to prices that already include the previous year’s. Three years at 4% multiply out to 1.04 cubed, a cumulative 12.49%. Over a decade the gap widens sharply: 4% a year for ten years is 48% cumulative, not 40%.
The rule of 70 gives a quick sense of the scale — dividing 70 by the inflation rate approximates the years for prices to double. At 4% that is about 18 years; at 7%, ten. Any long-horizon plan built by adding annual inflation rates rather than compounding them will understate the eventual price level substantially.
All three are correct, and they can point in different directions
Headline inflation covers the full basket. Core inflation strips out food and energy, whose prices are volatile and often driven by supply shocks rather than monetary conditions — central banks watch core because it is a better signal of persistent pressure. Neither is the rate any individual household faces.
Personal inflation depends on what you buy. A household spending a large share on rent and energy experiences something quite different from one whose spending is weighted toward electronics, where prices routinely fall. A single national rate is a weighted average across every household, and the dispersion around it is wide enough that most people are some distance from it.
A period rate, from an index with known biases
The rate computed here covers whatever interval separates the two readings — monthly, annual or anything else — and it is not annualised. Comparing a monthly rate against an annual one without converting is a straightforward error, and monthly figures are noisy enough that single readings rarely mean much.
Price indices themselves carry known measurement issues: substitution bias when consumers switch away from dearer goods, and quality adjustment, where a product improves while its price holds. Statistics agencies correct for both, imperfectly, and the residual is generally believed to overstate measured inflation modestly.
Frequently Asked Questions
What is the difference between inflation, disinflation, and deflation?
Inflation is a rising price level, so a positive rate. Disinflation is when that positive rate slows down, for example moving from 5% to 3%, but prices are still rising. Deflation is an outright fall in the price level, which shows up as a negative inflation rate.
What is the difference between headline and core inflation?
Headline inflation uses the full CPI, while core inflation is computed from a CPI that excludes volatile food and energy prices. Core inflation is often preferred for spotting the underlying trend because it is less jumpy month to month.
Why can a positive but falling inflation rate still mean prices are rising?
A falling rate is disinflation, not deflation. If the rate goes from 6% to 2%, prices are increasing more slowly, but they are still increasing. Prices only fall when the rate turns negative.
Is this the same as adjusting a dollar amount for inflation?
No. This calculator gives the inflation rate as a percentage change between two index readings. Adjusting a specific dollar value for inflation is a separate task that scales an amount by the ratio of two CPI levels rather than reporting the rate itself.
Can I use this for any two periods?
Yes, as long as both readings are from the same CPI series. You can measure month-over-month, quarter-over-quarter, or year-over-year inflation simply by choosing the appropriate initial and final values.
What does a negative result mean?
A negative inflation rate means the final CPI is lower than the initial CPI, signalling deflation, an actual decline in the average price level over the period.
Why divide by the initial CPI rather than the final one?
Inflation measures growth relative to the starting point, so the change is expressed as a fraction of where prices began. Dividing by the initial value is what makes it a true rate of change from that base.
Sources & References
Figures on this page are checked against primary, authoritative sources. Links open in a new tab.
Both CPI readings come from the same index series with a consistent base year.
The two periods are the intended start and end of the interval being measured.
The index values reflect comparable coverage and methodology across the two dates.
Where it stops
A single pair of readings captures only the chosen interval and may miss volatility within it.
The result inherits any basket, substitution, or quality biases present in the underlying CPI.
Comparing readings across a methodology change or rebasing can distort the computed rate.
Related Calculators
Real Interest RateThe exact Fisher real rate and the subtract-and-go approximation side by side, so the gap between them is visible.
GDP DeflatorThe broadest price index there is — nominal over real GDP — with the price change since the base year.
Purchasing PowerWhat a sum will still buy after years of inflation, and how much of its value has gone.
Personal Inflation RateYour own inflation rate from BLS price changes weighted by how you actually spend, against the official CPI-U figure.
ShrinkflationThe real price rise when a product shrinks: price per ounce, gram or sheet before and after, the way BLS counts it.
Fisher EquationSolve (1 + i) = (1 + r)(1 + π) for the nominal rate, the real rate or expected inflation, exactly.
Real WageTwo paychecks from different years compared in what they buy, on the US CPI-U, with the pay that would have kept pace and the real raise from any raise and inflation rate.
Federal Poverty LevelHousehold income as a percent of the 2026 or 2025 HHS poverty guidelines, with the income at 100% to 400% and common program lines.
Results are estimates for planning and analysis based on the figures you enter. They are not accounting, tax, or financial advice — verify with your own records and a qualified professional before making decisions.
Published the calculator with its formula, worked example, assumptions, limitations and a bespoke guide, and added an automated formula test suite covering it.
Property-tested that the rate is measured against the starting index rather than reported as a change in index points, which is the error the page exists to prevent.
Frequently Asked Questions now show on the page: 7 answers, checked in a page-by-page audit.
What the calculation assumes and where it stops now show on the page.
Add this calculator to your site
Responsive embed — and private: nothing your visitors type leaves their browser.