How does the inflation calculator project prices?
Inflation works like compound interest running against you. Each year's price increase applies to the previous year's higher price, so the effect builds on itself. The calculator applies one steady rate for every year you enter.
Future cost grows today's amount forward at that rate. Future value in today's dollars runs the same math in reverse, showing what a fixed sum would buy after prices rise. Total increase is the dollar gap between future cost and today's amount, and cumulative inflation expresses that gap as a percentage.
The rate you enter is an assumption. Published price indexes show what inflation has been; nobody knows what it will be, and individual categories such as health care, rent or electronics can move very differently from the overall average.
Future cost = A × (1 + i)^n Today's-dollar value = A ÷ (1 + i)^n Total increase = Future cost − A Cumulative inflation = ((1 + i)^n − 1) × 100
- A
- amount in today's dollars
- i
- assumed annual inflation rate, as a decimal
- n
- number of years
Example: replacing a $35,000 vehicle in 12 years
Scenario: Rosa expects to replace her car in 12 years. A comparable car costs $35,000 today, and she assumes prices rise 2.5% a year.
- Growth factor1.025^12 = 1.3448888
- Future cost$35,000 × 1.3448888 = $47,071.11
- Total increase$47,071.11 − $35,000 = $12,071.11
- Cumulative inflation(1.3448888 − 1) × 100 = 34.49%
- Today's-dollar value of $35,000 in 12 years$35,000 ÷ 1.3448888 = $26,024.46
A car costing $35,000 now would cost about $47,071.11 in 12 years at 2.5% inflation, a 34.49% increase.
Vehicle prices do not have to follow the overall inflation rate, so try a higher and lower rate to see a range.
When does an inflation projection help?
Setting a savings goal years away
Saving toward today's price for something you will buy in a decade leaves you short. Projecting the future cost gives a target in the dollars you will actually spend.
Judging whether savings are keeping up
If cash earns less than inflation, its buying power shrinks even as the balance grows. Comparing your interest rate with an assumed inflation rate shows the real result.
Testing a fixed income stream
A pension or annuity payment that never rises buys less every year. The today's-dollar value shows how much less.
Comparing prices across decades
Converting an old price into a rough today's-dollar equivalent puts historical costs on a more comparable footing.
What mistakes lead to bad inflation estimates?
Adding the rate instead of compounding it
Three percent for 20 years is not 60%; compounded, it is about 80.6%. The gap grows with time.
Assuming every price follows the average
Overall inflation is an average across many goods and services. Tuition, insurance or rent can rise much faster or slower than the headline rate.
Mixing real and nominal figures
A savings projection in future dollars should be compared with a future cost, not today's price. Pick one basis and keep every figure on it.
Using one unusual year as the long-run rate
A single high or low inflation year is a poor guide for decades. Running several rates gives a more honest range.
How much does a small change in the inflation rate matter?
Over long periods, a one-point difference in the assumed rate changes the result far more than intuition suggests. The table shows cumulative price growth at four steady rates, plus what $100 would buy after 30 years in today's terms.
The same math explains why long-term savings plans often use real returns. At 3% for 25 years, $100,000 kept in cash with no interest would buy what about $47,760.56 buys today.
| Annual rate | After 10 years | After 20 years | After 30 years | $100 in today's dollars after 30 years |
|---|---|---|---|---|
| 2% | 21.9% | 48.6% | 81.1% | $55.21 |
| 3% | 34.4% | 80.6% | 142.7% | $41.20 |
| 4% | 48.0% | 119.1% | 224.3% | $30.83 |
| 5% | 62.9% | 165.3% | 332.2% | $23.14 |
Terms used on this page
- Inflation
- Inflation is the general rise in prices over time, which reduces how much a dollar can buy. In the US it is most often measured by the Consumer Price Index, published monthly by the Bureau of Labor Statistics. When your savings earn less than inflation, their purchasing power shrinks even though the dollar balance grows.
- Real Rate of Return
- The real rate of return is what your money earns after adjusting for inflation. It shows the actual growth in purchasing power rather than in dollars. A quick estimate is the nominal rate minus inflation; the exact figure is (1 + nominal) ÷ (1 + inflation) − 1, which is slightly smaller.
- Compound Interest
- Compound interest is interest earned or charged on both the original principal and the interest that has already built up. Each period's interest is added to the balance, so the next period's interest is a little larger. Over long stretches, compounding makes savings grow faster and unpaid debts grow faster too.
- Rule of 72
- The Rule of 72 is a mental-math shortcut for estimating how long money takes to double at a fixed compound rate: divide 72 by the annual percentage rate. At 8%, money doubles in about nine years. It works best for rates between roughly 4% and 12% and can also estimate how fast debt or inflation doubles.
Inflation Impact Calculator: common questions
How much will something cost in 10 years with inflation?
Multiply today's price by (1 + inflation rate) raised to the 10th power. At an assumed 3% a year, the factor is about 1.344, so a $1,000 item would cost about $1,343.92. At 2% it would be about $1,218.99. The calculator does the exponent for you, and running two or three rates gives a reasonable range.
What is cumulative inflation?
It is the total percentage increase in prices over the whole period, not per year. Because each year's increase builds on the last, cumulative inflation is larger than the annual rate times the number of years. At 4% a year for 20 years, prices rise about 119.1% in total, not 80%.
What does future value in today's dollars mean?
It shows what a fixed sum would buy after the years you enter, expressed in current buying power. If you will receive $50,000 in 15 years and inflation averages 3%, that money will buy about what $32,093.10 buys today. It is a way to compare money received at different times on equal terms.
What inflation rate should I use?
Any rate you use is an assumption. Many people test a moderate central rate along with a higher and lower case to see the range. Official price index data from the Bureau of Labor Statistics shows what inflation has been historically, which can inform your choice, but past rates do not predict future ones.
How does inflation affect money in a savings account?
If the account's yield is below the inflation rate, your balance grows in dollars but loses buying power. The real return is roughly the interest rate minus inflation. A savings account earning 2% while prices rise 3% loses about 1% of buying power a year, even though the balance keeps rising.
What is the difference between nominal and real dollars?
Nominal dollars are face amounts at the time they are spent or received. Real dollars adjust for inflation to show purchasing power in a base year, usually today. This calculator's future cost is a nominal figure, while the today's-dollar value is a real figure. Comparing across years requires using one or the other consistently.
How long does it take prices to double?
Divide 72 by the annual inflation rate for a quick estimate. At 3%, prices double in about 24 years; at 4%, about 18 years. The exact figure with annual compounding is slightly different, and the rule of 72 calculator shows both side by side. At 2% inflation, the rule gives 36 years, and the exact figure with annual compounding is about 35.0 years.
Is the Consumer Price Index the same as my personal inflation rate?
Not necessarily. The CPI measures the average change in prices for a broad basket of goods and services bought by urban consumers. Your own spending mix may differ a lot: a renter, a homeowner with a fixed mortgage and a retiree with high medical costs can each experience different inflation from the same economy.
Can I use this calculator for deflation?
The math works with a negative rate, which would show falling prices and rising buying power. Sustained deflation across the economy is uncommon in the U.S., but prices for specific items, such as some electronics, often fall over time. Entering a negative rate for those categories can give a rough projection.
Sources
- Consumer Price Index — U.S. Bureau of Labor Statistics. Accessed October 17, 2026.
- I bonds — TreasuryDirect (U.S. Department of the Treasury). Accessed October 17, 2026.
- Compound interest (glossary) — U.S. Securities and Exchange Commission (Investor.gov). Accessed October 17, 2026.
We cite primary sources: regulators, central-bank data and federal agencies. Worked examples on this page are our own calculations, last checked October 17, 2026. See our methodology.