To project inflation, enter the dollar amount you have today, the annual inflation rate you want to assume, and the number of years into an Inflation Calculator; the tool returns two numbers that update instantly — the future price of the same basket of goods (future cost = amount × (1 + rate)^years) and what that cash will actually buy at the end of the period (future purchasing power = amount ÷ (1 + rate)^years). At a 3% annual rate over 10 years, for example, $100 today becomes a future cost of about $134.39 and a future purchasing power of about $74.41. The calculation is a single compound-inflation step applied to a constant rate you choose, so the same approach works whether you are sizing up a future expense, checking the real value of a savings balance, or stress-testing a long-term financial goal.
What the Calculator Asks For: Amount, Rate, and Years
The tool only needs three numbers from you and then it does the rest. The first is the dollar figure you want to track — a savings balance, a future tuition bill, an annual salary, or any amount you want to keep meaningful over a horizon. The second is the annual inflation rate you want to assume, written as a percentage, with the understanding that you can enter a negative value to model deflation. The third is the number of years you want to project over. Two of the inputs have a clear floor: the starting amount must be zero or positive, and the years must be zero or positive, so you cannot enter a negative horizon. The rate is the only input that can go either way, which is what lets the same tool handle both rising and falling prices. There is nothing to sign up for and nothing to configure — you type into the three boxes and the two outputs re-render the moment you change any value.
Running the Calculation: Enter Inputs and Read Outputs
The whole process from a blank form to a usable answer takes three steps, and the calculator does the compound math automatically.
- Enter the dollar value of the basket you want to track in the amount box — for example, 100 if you want to know what today's $100 will buy later.
- Enter the annual inflation rate you want to assume as a percentage (3 for 3%, 5 for 5%, or a negative number like -2 to model deflation) and then enter the number of years you want to project (for example, 10).
- Read the two outputs the calculator displays: future cost, which is what today's amount will cost in the future, and future purchasing power, which is what today's cash will actually buy at the end of the period. Both update instantly as you change any input, so you can adjust the rate or the years to compare scenarios side by side.
Choosing the Right Inflation Rate to Plug In
Because the calculator assumes a single constant rate for the entire horizon, the number you type in drives the entire result. Pick a rate that is too low and you will understate how much a future expense will cost; pick one that is too high and you will overstate the erosion of a cash balance. A common anchor is the long-run average change in a broad consumer price index, which captures the general rise in what households pay for goods and services (see Inflation on Wikipedia). Different goods inflate at different speeds over a given period — housing and education, for example, have historically outpaced overall measures in many countries — which is one reason stress-testing with more than one rate is usually smarter than betting everything on a single figure. Try a low, a middle, and a high rate (say 2%, 4%, and 6%) and watch how the two outputs move in opposite directions; that range will give you a feel for the spread between best-case and worst-case projections without needing real historical data behind the calculation.
Future Cost vs. Future Purchasing Power: Which Number Do You Want?
The two outputs are the inverse of each other and are useful for different questions. Future cost answers the forward-looking question — "what will something that costs $X today cost in N years?" — by multiplying the amount by (1 + rate)^years. Future purchasing power answers the reverse question — "what will $X of cash actually buy in N years, measured in today's prices?" — by dividing the amount by the same factor. A simple table makes the contrast obvious.
| Output | Question it answers | Formula | Direction as years grow (positive rate) |
|---|---|---|---|
| Future cost | What will today's amount cost in the future? | amount × (1 + r)^n | Rises |
| Future purchasing power | What will today's cash actually buy in today's prices? | amount ÷ (1 + r)^n | Falls |
Use future cost when you are sizing up a future bill — a down payment, a college bill, a wedding — that is denominated in future dollars. Use future purchasing power when you want to translate a future nominal sum back into today's prices, such as when you are checking whether a projected retirement balance will keep up with living costs. If you want to compare the two perspectives for the same scenario, see this Inflation Calculator alternative: two answers, one tool walkthrough.
Modeling Deflation With a Negative Rate
The same calculator handles deflation without any special mode — you just enter a negative annual rate, such as -2%. With a negative rate, (1 + r) becomes smaller than one, so the compound factor shrinks instead of growing. Future cost falls below your starting amount (a basket that costs $100 today would cost less tomorrow) and future purchasing power rises above it (each dollar will stretch further). The amount and years still must be zero or positive, so the horizon cannot go negative — only the rate can. This is a quick way to check how a sustained deflationary environment would reshape a long-term plan. For a more detailed look at the mechanics, the Can You Model Deflation With a Negative Rate? guide walks through the same idea with several sample numbers.
How the Two Outputs Compound Over Longer Horizons
Because the formula uses exponentiation, doubling the number of years does more than double the gap between the two outputs — it multiplies the compounding effect. At 3% inflation, ten years of compounding pushes future cost up by about a third and pulls future purchasing power down by roughly a quarter; twenty years roughly doubles future cost and pulls future purchasing power down to about 55 cents on the dollar; thirty years more than doubles the original price tag and cuts purchasing power to a little over 40 cents on the dollar. The same pattern holds for any positive rate you choose: small differences in the assumed percentage look modest over a five-year horizon but become dramatic over a thirty-year horizon. That compounding sensitivity is why the calculator is most useful as a comparison tool — type in 2%, then 4%, then 6% over the same twenty- or thirty-year horizon and watch both outputs swing, rather than fixating on a single point estimate. If you only have time to do one sanity check, lengthen the years and ask yourself whether the resulting gap still feels plausible for the question on the table; if not, the assumed rate is probably too aggressive for that scenario.
What the Calculator Does Not Do
The tool is built around one fixed annual rate, not historical inflation data. Real inflation, as tracked by indexes such as the Consumer Price Index (CPI), rises and falls over time, so the actual outcome over a multi-year horizon will almost always differ from a single-rate projection (see real versus nominal value in economics). The calculator is best used to build intuition, compare a small set of scenarios, and stress-test a number — not to predict an exact price. Because the result depends entirely on the rate you type in, treat the output as a starting point and confirm any decision with a licensed financial professional. Everything runs in your browser, no data leaves your device, and there is no sign-up or account to create.