Inflation Calculator — Step-by-Step Solutions
The Inflation Calculator helps you understand how inflation affects the value of money over time. Using US CPI-U data from the Bureau of Labor Statistics (1913 to 2025), it calculates purchasing power equivalents, cumulative and annualised inflation rates, and the real value of money in the future.
Four modes cover the most common inflation questions: what an amount from one year would be worth in another, the inflation rate between two years, how inflation erodes future purchasing power, and a side-by-side comparison of purchasing power across multiple decades.
CPI data source: US Bureau of Labor Statistics (CPI-U annual averages, 1913-2025). For educational purposes only. Not financial advice.
Your calculations will appear here
How to Use the Inflation Calculator
- Select a mode using the tabs at the top: Purchasing Power, Inflation Rate, Future Value, or Compare Years.
- For Purchasing Power, enter a dollar amount and the start and end years.
- For Inflation Rate, enter two years to see the cumulative and annualised rate.
- For Future Value, enter a present value, expected inflation rate, and number of years.
- For Compare Years, enter an amount and a base year to see equivalent values across decades.
Formula and Theory
Inflation measures the rate at which prices rise, causing purchasing power to fall. The Consumer Price Index (CPI-U) is the most widely used measure of inflation in the United States, published by the Bureau of Labor Statistics.
The CPI tracks the cost of a representative basket of consumer goods and services over time. The formula is: Adjusted Amount = Original Amount x (CPI_end / CPI_start).
The annualised inflation rate converts cumulative inflation into a per-year average using geometric mean: Annual Rate = (CPI_end / CPI_start)^(1/years) - 1.
Historically, US inflation has averaged roughly 3% per year since 1913, though individual decades have varied widely.
Worked Examples
Example 1: Purchasing power of $100 from 1990
Problem: What would $100 from 1990 be worth in 2025?
Solution: CPI 1990 = 130.7, CPI 2025 = 320.0. Adjusted = $100 x (320.0 / 130.7) = $244.84.
Answer: $244.84 in 2025
Example 2: Inflation rate over a decade
Problem: What was the cumulative inflation from 2010 to 2020?
Solution: CPI 2010 = 218.1, CPI 2020 = 258.8. Cumulative = 18.66%. Annualised = 1.72%.
Answer: 18.66% cumulative, 1.72% annualised
Example 3: Future purchasing power loss
Problem: If inflation averages 3% per year, what will $1,000 buy in 20 years?
Solution: Real value = $1,000 / (1.03)^20 = $553.68.
Answer: $553.68 in today's purchasing power
Frequently Asked Questions
What is the CPI and where does the data come from?
Is this calculator accurate for countries outside the US?
Why does the calculator only go back to 1913?
What is the difference between cumulative and annualised inflation?
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