What Is Inflation?

Inflation is a sustained increase in the general level of prices for goods and services over time. When inflation is positive, each unit of currency buys a little less than it did before — economists say the purchasing power of money falls.

Whether you are buying groceries, negotiating a salary or saving for retirement, inflation quietly shapes what your money can do. This guide explains how inflation is measured, what causes it, how central banks try to control it, who it helps and hurts, and what you can do to protect your finances — in plain language, with no economics degree required.

How inflation is measured

Governments and statistical agencies track inflation using price indexes. The best known is the Consumer Price Index (CPI), which follows the price of a representative "basket" of everyday goods and services — food, housing, transport, healthcare and more. Statisticians survey thousands of prices regularly, weight them by how much households actually spend, and publish the index monthly. The annual percentage change in the index is reported as the inflation rate.

There are several related measures worth knowing:

• Core inflation strips out volatile food and energy prices to reveal the underlying trend — policymakers watch it closely because it is less noisy.
• Producer Price Index (PPI) tracks prices at the wholesale level and can foreshadow consumer inflation, since rising producer costs often get passed on.
• PCE price index is the US Federal Reserve's preferred gauge; it adjusts as consumers substitute cheaper alternatives.
• Some countries publish their own variants, such as the UK's CPIH (which includes housing costs) or India's CPI combined index.

A simple example: the shrinking shopping basket

Imagine a basket of weekly groceries costs 100 currency units today. With steady 3% annual inflation, that same basket costs about 103 next year — and roughly 134 after ten years, because inflation compounds like interest in reverse. (Our guide to compound interest explains the same mathematics working in your favour.)

A handy shortcut is the rule of 72: divide 72 by the inflation rate to estimate how many years it takes for prices to double — and your money's purchasing power to halve. At 2% inflation, that is about 36 years; at 7%, just over 10. Small differences in the rate matter enormously over a lifetime.

What causes inflation?

Economists commonly describe two broad forces. Demand-pull inflation happens when spending grows faster than the economy's ability to produce, bidding prices up — for example, when a strong job market puts more money in people's pockets, or large government stimulus boosts demand. Cost-push inflation happens when the costs of production rise — for example, more expensive energy or raw materials — and businesses pass those costs on. The oil price shocks of the 1970s and the post-pandemic supply-chain disruptions are classic cost-push episodes.

Expectations matter too: if people expect prices to rise, workers may seek higher wages and firms may raise prices pre-emptively, which can reinforce the cycle — a dynamic sometimes called a wage-price spiral. Some economists also emphasize the role of money supply growth, arguing that when money grows much faster than real output over long periods, inflation tends to follow. In practice, most episodes involve a mix of these forces, which is why diagnosing inflation in real time is genuinely difficult.

Hyperinflation: when prices spiral out of control

Hyperinflation is inflation so rapid that money quickly loses meaning — economists often use 50% per month as the benchmark definition. Famous episodes include Weimar Germany in the 1920s, Zimbabwe in the late 2000s and Venezuela in the 2010s. In the worst cases, prices can double within days, people need wheelbarrows of cash for ordinary shopping, and savings are effectively wiped out.

Hyperinflation almost always follows a breakdown of confidence — typically when governments facing crises create money on a massive scale to cover spending, and citizens rush to spend currency before it loses value, accelerating the spiral. It is a monetary catastrophe, not a normal business-cycle event, and it underscores why stable institutions and credible central banks matter.

The opposites: disinflation and deflation

Two related terms cause frequent confusion:

• Disinflation means inflation is slowing down but still positive — prices keep rising, just more slowly. This is usually welcome news.
• Deflation means prices are actually falling across the economy. It sounds pleasant, but economists fear it: consumers delay purchases expecting lower prices, debts grow heavier in real terms, and wages resist cuts — a combination that can trap an economy in a deflationary spiral. Japan's experience in the 1990s and 2000s is the textbook example of how hard deflation is to escape.

Why central banks target low, stable inflation

Most central banks in advanced economies aim for low and stable inflation — commonly around two percent a year — rather than zero. The US Federal Reserve, the European Central Bank and the Bank of England all use versions of a 2% target. A little inflation gives policymakers room to cut interest rates in downturns, helps wages and prices adjust without nominal cuts, and provides a buffer against dangerous deflation.

Their main tool is interest rates. When inflation runs too hot, central banks raise rates: borrowing becomes expensive, spending and hiring cool, and price pressures ease. When the economy is weak, they cut rates to encourage borrowing and spending. High or unpredictable inflation, by contrast, erodes savings, distorts investment decisions and tends to hurt people on fixed incomes most — which is why central banks guard their credibility on inflation so fiercely. Broader measures of economic health, like GDP, are read alongside inflation data when policymakers make these calls.

Winners and losers: how inflation affects different people

Protecting your money from inflation

You cannot control inflation, but you can plan around it. Keeping some cash for emergencies is essential, but money left idle for years is guaranteed to lose purchasing power — which is why financial planning usually compares investment returns after inflation, not before. Common strategies people use include investing for the long term in diversified assets, since productive assets have historically outpaced inflation over long horizons; building a realistic budget (our 50/30/20 budget guide is a good starting point); and, in some countries, buying inflation-linked government bonds whose payouts rise with prices.

Understanding the basic building blocks helps too: our explainers on stocks vs. bonds and credit scores cover concepts that come up in almost every inflation conversation.

This article is general educational information, not financial advice.