Quick answer
Future cost = amount × (1 + rate)^years, and the purchasing power of today's money = amount ÷ (1 + rate)^years. At 3% inflation for 10 years, $100 today costs $134.39 then, and $100 will buy only what $74.41 buys today.
Enter an amount, an average annual inflation rate and a number of years. The calculator returns the future cost and the purchasing power.
Related tools: Savings Calculator: Savings balance with regular monthly deposits. CD Ladder Calculator: Maturity values of a ladder of equal CDs with 1, 2, 3 … year terms. Emergency Fund Calculator: Emergency fund target and time to reach it.
How to use the Inflation Calculator
- Enter amount today ($) (0 or more).
- Enter average annual inflation (%) (between -50 and 100). It starts at 3.
- Enter years (between 0 and 100).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Amount today | A number, in $ | ≥ 0 |
| Average annual inflation | A number, in % | ≥ -50, ≤ 100, starts at 3 |
| Years | A number | ≥ 0, ≤ 100 |
Formula and method
Formula
future cost = amount × (1 + rate)^years; purchasing power = amount ÷ (1 + rate)^years
IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice.
Uses your assumed constant rate; it does not use historical CPI data.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Amount today = 100; Average annual inflation = 3; Years = 10.
| Result | Value |
|---|---|
| Future cost | $134.39 |
| Purchasing power of today's amount | $74.41 |
Example 2
Inputs: Amount today = 100; Average annual inflation = 0; Years = 10.
| Result | Value |
|---|---|
| Future cost | $100.00 |
| Purchasing power of today's amount | $100.00 |
The first line is the headline result (future cost). Below it the inflation Calculator lists purchasing power of today's amount, which describe the same case from other angles. IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice.
Compounding
Inflation compounds like interest: 1.03^10 = 1.3439. A handy shortcut is the rule of 72: at 3% prices double in about 72 ÷ 3 = 24 years.
Flat rate, not historical data
This page applies one steady rate. Real inflation varies year to year; for actual past price changes use a CPI-based calculator. A negative rate models deflation.
How the result changes with amount today
Holding every other input at the first worked example, this table changes only amount today. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Amount today | Future cost | Purchasing power of today's amount |
|---|---|---|
| 50 | $67.20 | $37.20 |
| 100 | $134.39 | $74.41 |
| 200 | $268.78 | $148.82 |
| 400 | $537.57 | $297.64 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Years: entering "-1" shows "Years must be at least 0." beside that field and no result.
Choosing between the Inflation Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Savings Calculator](/finance/savings-calculator/) | initial amount, annual interest rate and years | Savings balance |
| [CD Ladder Calculator](/finance/cd-ladder-calculator/) | total to invest and aPY of each rung | Total at maturity |
| [Emergency Fund Calculator](/finance/emergency-fund-calculator/) | essential monthly expenses and months of cover | Emergency fund target |
| [Savings Goal Calculator](/finance/savings-goal-calculator/) | savings goal, current savings and annual return | Monthly deposit needed |
| [Auto Loan Calculator](/finance/auto-loan-calculator/) | vehicle price, down payment and interest rate | Monthly payment |
Background: interest, saving and investing
A nominal rate (APR) does not include the effect of compounding; the annual percentage yield (APY) does: APY = (1 + r/n)^n − 1. A 5% nominal rate compounded annually is 5.000%, semi-annually about 5.063%, quarterly about 5.095% and monthly about 5.116%, so more frequent compounding helps, but with diminishing returns.
The rate you enter in a projection is an assumption, not a promise: real returns vary and can be negative. Fees and taxes are not modelled unless the page says so.
Assumptions and limitations
- Negative rates model deflation
Results are estimates for planning, not financial advice. Lender terms, fees, taxes and rounding rules can change real figures, so confirm important numbers with your lender or a licensed adviser.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for years to confirm this.
Frequently asked questions
What inflation rate should I use?
Central banks often target about 2%; past averages vary by country and period.
How do I find real returns?
Subtract inflation from your nominal return, or compute (1 + r) ÷ (1 + i) − 1.
Does it use CPI data?
No, it uses the rate you enter.
What does the Inflation Calculator calculate?
Future cost or purchasing power using an average inflation rate you provide. It returns Future cost and Purchasing power of today's amount.
What formula does the Inflation Calculator use?
future cost = amount × (1 + rate)^years; purchasing power = amount ÷ (1 + rate)^years. Uses your assumed constant rate; it does not use historical CPI data.
What do I need to enter in the inflation Calculator?
You enter Amount today ($), Average annual inflation (%) and Years.
How is the result rounded or limited?
IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice. Negative rates model deflation.
What is an example of a inflation result?
With amount today 100, average annual inflation 3 and years 10, the future cost is $134.39.
Can I rely on this calculator for a decision?
Results are estimates for planning, not financial advice. Lender terms, fees, taxes and rounding rules can change real figures, so confirm important numbers with your lender or a licensed adviser. For this calculator in particular: Negative rates model deflation.
Related calculators
- Savings Calculator — Savings balance with regular monthly deposits.
- CD Ladder Calculator — Maturity values of a ladder of equal CDs with 1, 2, 3 … year terms.
- Emergency Fund Calculator — Emergency fund target and time to reach it.
- Savings Goal Calculator — Monthly deposit needed to reach a savings goal.
- Auto Loan Calculator — Monthly car payment after down payment and trade-in.
- Amortization Calculator — Full amortization schedule with optional extra monthly payments.
Sources
- Standard time-value-of-money relations (e.g. Brealey, Myers & Allen, Principles of Corporate Finance)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.