Free inflation calculator

How inflation erodes the value of money

Inflation is the slow rise in the general level of prices, and it works against your money one year at a time. Economists measure it with the Consumer Price Index (CPI), the government’s tally of what a fixed basket of everyday goods and services — groceries, rent, gas, healthcare, insurance — costs from one period to the next. When that index rises, the purchasing power of a dollar falls: the bill in your pocket still says $1, but it buys a little less than it did before.

The reason inflation matters so much over a lifetime is that it compounds. A loss of a few percent each year stacks on top of the year before, the same way interest builds in a savings account — only in reverse. Over a long-run average of about 3% a year (a typical figure, though it swings well above and below that depending on the decade), prices roughly double every 24 years or so. Money left sitting in a zero-interest account does not stay still in real terms; it quietly shrinks while the number on the statement never changes.

How to use this inflation calculator

This tool works in two directions, so you can look backward or forward.

Past to today (the time machine). Use the first card to translate old money into today’s dollars. Type an amount, pick the year it came from, and the calculator scales it by the change in CPI between then and now. This answers questions like “what would my grandfather’s salary be worth today?” or “has my pay actually kept up since 2015?” Read the result as the amount you’d need now to match that old purchasing power.

Today to the future (cash erosion). Use the second card to project what a sum of cash will buy down the road. Enter an amount, choose how many years ahead, and set an annual inflation rate — the field defaults to roughly the latest reading, but you can raise or lower it to test a more cautious or optimistic scenario. The output shows the same dollars expressed in today’s buying power, plus how much of that value inflation eats away.

A worked example

Say you want to know what $1,000 from the year 2000 is worth today. Prices have risen by a large margin since then, so the time machine shows that it takes well over $1,800 now to buy what that $1,000 bought back then — your money had to grow by more than 80% just to break even on purchasing power.

Now look forward. Suppose you park $10,000 in a drawer for 20 years and assume a steady 3% inflation rate. The erosion card shows that the same $10,000 will buy only about $5,500 worth of goods in today’s terms — almost half its purchasing power gone, even though the cash itself never moved. That gap is the cost of letting money sit idle.

Terms to know

• CPI (Consumer Price Index). The benchmark index that tracks the cost of a representative basket of goods and services. Inflation is the percentage change in the CPI over time.
• Purchasing power. What your money can actually buy. Rising prices lower it; a raise or interest can restore it.
• Real vs. nominal. A nominal figure is the face value in dollars; a real figure is adjusted for inflation. Your savings can grow in nominal terms while shrinking in real terms.
• Cumulative vs. annual inflation. Annual inflation is one year’s price change; cumulative inflation is the total stacked-up change across many years, which is always larger because it compounds.

Common mistakes to avoid

Assuming your inflation equals the headline rate. The CPI describes an average household. Your personal inflation depends on what you actually buy — if a big share of your budget goes to rent, tuition, or medical care, your real rate can run higher than the number in the news.

Ignoring inflation on long-term savings. A balance that feels safe in cash is steadily losing ground if it earns less than the inflation rate. The longer the time horizon, the larger the hidden loss.

Confusing real and nominal returns. An account paying 4% while inflation runs 3% is only earning about 1% in real terms. Always subtract inflation before deciding whether an investment is truly getting ahead.

Related tools and guides

• Compare safe places to grow cash above inflation with the where to park cash tool.
• Check whether a pay bump actually beats rising prices using the raise vs. inflation calculator.
• Convert between currencies at live rates with the currency converter.
• Browse every free calculator on the site in the calculators library.
• Read the guides on common money mistakes and how to avoid them and wealth-building financial planning strategies to put these numbers to work.

This calculator is for general education, not financial advice. Inflation varies over time and by household, so treat any single rate as an estimate rather than a promise.