Inflation Calculator

What Is Inflation and What Does an Inflation Calculator Do?

What is inflation? Inflation is the steady rise in the general price level over time, which means each unit of money buys a little less than before. So what does inflation mean for you in practice — it means a fixed amount of cash slowly loses value. An inflation calculator measures exactly how much, using the Consumer Price Index (CPI). Enter an amount and a start date, and it shows what that money is worth today, the inflation rate, the multiplier, and the purchasing power loss. This tool supports multiple currencies, each with its own official data source: BLS CPI-U for US Dollar, Eurostat HICP for Euro, and ONS CPI for British Pound.

How to Calculate Inflation: The CPI Formula

Here is exactly how to calculate inflation: the inflation rate is the percentage change in the CPI between two periods. So if you have ever asked what is the inflation rate between two dates, this is the formula behind the answer:

Inflation rate = ((End CPI - Start CPI) / Start CPI) x 100

The inflation multiplier is simply the end CPI divided by the start CPI. For example, if the index was 100 at the start and 250 at the end, the multiplier is 2.5x and the rate is 150%. The inflation difference between any two months — useful as an inflation difference calculator — is found the same way. The tool reads the official CPI for the months you choose and does this automatically.

Purchasing Power Loss

Rising prices erode purchasing power — the amount of goods a unit of currency can buy. The formula:

• Purchasing power loss = (1 - 1/Multiplier) x 100
• A 2x multiplier means a 50% loss — your money buys half as much.
• A 10x multiplier means a 90% loss — you need 10 times as much for the same purchase.

This is why a fixed amount of cash held over decades buys far less than it did originally, while assets that grow with or above inflation preserve value.

Official CPI Data Sources by Currency

Value of Money Calculator: Two Modes

Acting as a value of money calculator (also called a money value calculator), the tool offers two modes:

• Past to Now: Enter a past amount and date to see what it is worth in today's money.
• Between Two Dates: Compare any two periods to see the inflation rate and how the amount changed between them.

For example, the value of $100 from 1990 in today's money, or the cumulative change between January 2000 and January 2024, is computed instantly from official CPI data.

Annual Inflation, Monthly Inflation and Inflation Expectation

Two figures are reported most often. Annual inflation is the 12-month change in the CPI — the headline rate you see in the news. Monthly inflation is the change from one month to the next, which tends to be volatile because of seasonal effects: food prices often ease in summer, while rent, services and energy can push the monthly figure up early in the year. To see annual inflation in the tool, select a 12-month gap in "Between Two Dates"; for monthly inflation, select two consecutive months.

Inflation expectation is different again: it is what households, businesses and central banks predict prices will do in the months ahead. While this calculator works with realised, official CPI data rather than forecasts, comparing past annual inflation rates with current expectation surveys helps you judge whether price pressure is rising or easing.

Dollar Inflation Calculator: Value Across Decades

Used as a dollar inflation calculator, the tool shows how the US Dollar has lost value over long periods. Because of dollar inflation, $100 in 1980 has the buying power of several hundred dollars today. Select USD, enter the original year and amount, and the BLS CPI-U data converts it to today's money instantly — handy for comparing historical salaries, house prices or product costs in real terms.

Why It Matters

Understanding price changes helps with salary negotiations, retirement planning, investment decisions and historical comparisons. If your raise is below the headline rate, your real income falls even though the nominal number rises. Comparing prices across years — a house, a salary, a product — is only meaningful when adjusted for the change in money's value. This tool makes those adjustments with official CPI data so the comparison is accurate.

How to Use This Inflation Calculator

Select a currency (USD, EUR, GBP or TRY) — each uses its own official CPI. In Past to Now mode, choose a start year and month and enter an amount to see its value today. In Between Two Dates mode, choose both a start and end date. Press calculate to get the inflation rate, multiplier, value and purchasing power loss. See the FAQ below for the formulas and data sources.