Inflation Calculator

Enter an amount, the annual inflation rate you expect, and a number of years. The calculator projects what a purchase costing that amount today will cost at the end of the period, what the same money will still buy, and the total rise in prices along the way. It runs entirely in your browser and updates as you type.

How the projection works

Prices compound the same way interest does, so the math here is the standard compound interest formula applied to a price instead of a balance:

future = amount × (1 + r ÷ 100)^y

A rate quoted per year is applied to a base that already contains last year's rise, which is why the effect accelerates: a steady 3.2% adds a little more currency each year than the year before. Purchasing power is the mirror image, the same amount divided by the growth factor rather than multiplied by it, because if the price level is 37% higher then each unit of money commands proportionally less.

With the defaults — 1,000 at 3.2% over 10 years — the growth factor is 1.032¹⁰ = 1.3702. A purchase costing 1,000 today is projected to cost 1,370.24, today's 1,000 will stretch only as far as 729.80 does now, and prices overall rise 37.0%. Notice the asymmetry: prices climb 37% but buying power falls just 27%, because the two percentages are measured against different bases.

Measuring a moving price level

Inflation only means something once you can measure the general price level, and that is a harder problem than tracking any single good. The first serious attempt in English is usually credited to William Fleetwood, a clergyman who became Bishop of St Asaph in 1708 and Bishop of Ely in 1714. His Chronicon Preciosum, published anonymously in 1707, built an index of averaged price relatives to answer a practical question. An Oxford college statute of 1440 capped a fellow's outside income at five pounds, and Fleetwood set out to establish what five pounds in 1440 would be worth in his own day. Rice Vaughan's A Discourse of Coin and Coinage, published posthumously in 1675 and edited by the poet Henry Vaughan, holds the earliest known work on changes in the price level, but Fleetwood produced something closer to a modern index number.

The technique matured over the next two hundred years. In 1764 the Italian economist Gian Rinaldo Carli averaged the price relatives of grain, wine and oil to set prices around 1500 against prices around 1750, a simple arithmetic mean that, as later statisticians pointed out, overweights the largest increases. The two formulas still taught today arrived in the 1870s in Germany. Étienne Laspeyres, in 1871, priced a fixed basket of base-period quantities at new prices; Hermann Paasche, in 1874, used current-period quantities instead. A Laspeyres index tends to overstate inflation and a Paasche index to understate it, because neither fully captures how shoppers substitute away from whatever has grown dear. Irving Fisher made the case for the geometric mean of the two in The Making of Index Numbers of 1922, and the label he attached to it, the ideal index, stuck.

Official statistics agencies put these ideas to work under wartime pressure. The United States Consumer Price Index grew out of studies of workers' living costs during the First World War, when prices in shipbuilding centres rose fast enough to make wage adjustments a live dispute. The Bureau of Labor Statistics published separate indexes for 32 cities in 1919, began a regular national index in 1921, and later estimated the series back to 1913 from food-price records. That 1913 baseline is why so many US inflation comparisons still start there.

From clipped coins to inflation targets

Rising prices are far older than any index. Roman emperors debased the silver coinage by degrees: Nero's reform of AD 64 cut the denarius to roughly 94% fine, and by the middle of the third century the workhorse silver coin, the antoninianus, had become copper under a thin silver wash, so it took more coins to buy the same goods. When prices spiralled at the end of the third century, Diocletian answered in 301 with an edict setting maximum prices, an early and poorly enforced demonstration that decree does not repeal supply and demand. The word inflation is far newer in this sense. It descends from the Latin inflare, to blow into, and its monetary use is recorded in American English by 1838, then spread during the American Civil War, when the quantity of paper banknotes outran the metal available to redeem them and observers spoke of an inflated currency. That early sense described a currency swollen with paper rather than the price of goods rising; the shift to the modern meaning came later.

Economists had long suspected the link between the quantity of money and the level of prices — David Hume argued it in his essay Of Money of 1752, and David Ricardo pressed the case in The High Price of Bullion of 1810 — but the modern policy response is recent. New Zealand went first: a Reserve Bank Act passed in 1989 was followed in March 1990 by a Policy Targets Agreement committing the bank to a published range of 0 to 2%. Canada adopted a target in 1991 and the United Kingdom in 1992, and most major central banks had followed by the end of the decade. The specific rates they aim for shape the figure you should type into this tool.

One constant rate, no CPI lookup

This tool projects at the single rate you give it. It does not fetch historical CPI figures, and it cannot tell you what 50 in 1985 equals today — for that, use the official series: the BLS inflation calculator in the US, the ONS in the UK, Eurostat for the euro area, Statistics Canada, or the ABS in Australia. A constant rate is a simplification, but for forward planning it is the only workable assumption, since future CPI is unknown.

What rate to plug in

The Federal Reserve, the Bank of England, the ECB and the Bank of Canada all target 2% inflation; the Reserve Bank of Australia targets a 2–3% band. Actual inflation wanders around those targets. US CPI averaged roughly 1.8% through the 2010s, then peaked at 9.1% in June 2022 before falling back. The 3.2% default sits between the target and the recent past. If a projection would change a real decision, run it again at 2% and at 4% and look at the range rather than a single number.

The rule of 72

For a quick head check, divide 72 by the rate to estimate how many years prices take to double. The shortcut appears in print as early as Luca Pacioli's Summa de arithmetica, printed in Venice in 1494, which states it without any derivation, so it was probably already in circulation among merchants. It holds up well at everyday rates:

At the default 3.2%, prices double roughly every 22 years — a useful sanity check against the 37% rise the calculator reports for 10.

A constant-rate projection is a planning aid, not a forecast of what prices will actually do. See the site disclaimer.

Frequently asked questions

What will 1,000 be worth in 10 years?

At 3.2% a year, prices rise about 37% over a decade, so 1,000 will buy roughly what 730 buys today. Flip it around and a purchase priced at 1,000 now is projected to cost about 1,370 in 2036. At the 2% rate most central banks target, the same 1,000 keeps about 820 of its buying power.

What inflation rate should I use for long-term planning?

The central banks of the US, UK, eurozone and Canada all target 2%, and Australia targets a 2 to 3% band, so 2 to 3% is a defensible planning range. Actual results stray from targets: US CPI averaged roughly 1.8% through the 2010s and then hit 9.1% in June 2022. Many planners run the numbers twice, once at 2% and once at 4%, and treat the spread as the honest answer.

How long until prices double at 3% inflation?

The rule of 72 says roughly 72 divided by 3, or 24 years. The exact answer is ln 2 divided by ln 1.03, which works out to 23.4 years, so the shortcut lands within a year. At 6% the doubling time drops to about 12 years, which is why even moderate inflation compounds into large changes over a working life.

Does this inflation calculator use historical CPI data?

No. It projects forward at one constant rate that you choose, which is the only workable approach for the future since nobody knows the next decade of CPI. For the past, such as what 100 in 1990 equals today, use the official series instead: the BLS calculator for the US, the ONS for the UK, or Eurostat for the euro area.