Purchasing Power Calculator

A purchasing power calculator converts a future dollar amount into today's dollars so you can see what it will actually buy. Inflation does not shrink the number in your account, it shrinks what that number is worth. At 3% average inflation, $100,000 held for 10 years has the buying power of about $74,409 in today's terms, a loss of roughly 25.6% even though the balance never fell.

That distinction is the whole point of this page. A savings balance, a fixed pension, a structured settlement or a cash reserve all keep the same face value while the price level moves underneath them. This tool measures the gap: how much real value a sum loses, how many extra dollars you would need at the end to break even, and how fast the erosion accelerates as the horizon lengthens.

How purchasing power is calculated

Two mirror-image formulas do all the work. The first converts a future sum into today's dollars, the second converts today's cost into the dollars you would need later:

Here i is the average annual inflation rate written as a decimal (3% becomes 0.03) and n is the number of years. The term (1 + i)ⁿ is the price multiplier: it tells you how many times more expensive the same basket of goods becomes. Divide by it to move money backwards into today's dollars, multiply by it to move today's prices forward.

The percentage of value lost follows directly: Loss % = (1 − 1 ÷ (1 + i)n) × 100. Notice this is not the same as the cumulative price increase. If prices rise 80%, buying power does not fall 80%, it falls by 1 − 1/1.80, which is about 44%. Confusing the two is the single most common mistake people make with inflation math.

Worked example: $50,000 for 20 years at 3%

Suppose you are holding $50,000 that you do not plan to touch for 20 years, and you assume a long-run average inflation rate of 3%. Step by step:

1. Compute the price multiplier: (1 + 0.03)²⁰ = 1.806111. Prices roughly 1.81x over the period.
2. Divide the amount by the multiplier: 50,000 ÷ 1.806111 = $27,684. That is what the money buys, in today's terms, at the end of year 20.
3. Subtract to get the loss: 50,000 − 27,684 = $22,316 of buying power gone, which is 44.6% of the starting value.
4. Multiply instead of dividing for the break-even target: 50,000 × 1.806111 = $90,306. You would need that much in year 20 to buy what $50,000 buys today, meaning $40,306 more than you started with.

The erosion is not linear. The same $50,000 is still worth $43,130 after 5 years and $37,205 after 10, then drops to $32,093 by year 15 and $27,684 by year 20. Compounding does its damage late, which is exactly why long horizons deserve the most attention.

Buying power of $10,000 by rate and horizon

The table below applies the same formula to a round $10,000. Read down a column to see how a single rate compounds, and read across a row to see how much the assumed rate matters. All figures are in today's dollars.

Because the formula is proportional, you can scale any row: at 3% over 20 years a dollar keeps about 55.4 cents, so $250,000 would keep about $138,419 of buying power. The percentages in the next table are the version of this that never needs scaling.

Loss of value table: percent of buying power gone

This is the same math expressed as a percentage, which makes it independent of the amount. It applies equally to $500 and to $5 million.

Two numbers in that grid deserve a second look. At the Federal Reserve's 2% long-run target, a 30-year retirement still costs you nearly half of every unindexed dollar. And at 6%, a rate U.S. consumer inflation exceeded in the early 1980s and again in 2022, more than two thirds of the value is gone within 20 years.

Dollars needed later to match today

Flip the formula and you get a savings target rather than a warning. This table shows what a future balance has to reach just to buy what $10,000 buys today, before any real gain counts.

How to use this calculator

1. Pick a view. Choose What it will be worth when you already hold the money, or What I will need when you are setting a future target. Both numbers are always shown, only the headline changes.
2. Enter the amount today. Use the actual sum: a savings balance, a monthly pension payment, a settlement, a college cost, a salary. The math works the same on any figure.
3. Set an average annual inflation rate. The shortcut buttons cover 2%, 3%, 4% and 6%, and you can type any value in between. Run more than one.
4. Choose the number of years. Use the quick picks or type an exact horizon up to 100 years.
5. Read the result. The headline gives the answer for your chosen view, the four tiles give the loss in dollars and percent plus the mirror figure, and the tables below show the path year by year and the spread across four rates.

Who this calculator is for

• Savers holding cash who want to see the cost of leaving money in a low-yield or no-yield account.
• Retirees and near-retirees checking whether a fixed pension or annuity without a cost-of-living adjustment will still cover the bills in 20 years.
• Parents saving for college who need a future tuition target rather than today's sticker price.
• Anyone weighing a lump sum against payments over time, where the later dollars must be converted into today's dollars before the comparison means anything.
• Employees judging a raise, since a raise below the inflation rate is a real pay cut even though the paycheck is bigger.
• Investors deciding what nominal return is actually needed to make progress instead of standing still.

Second worked example: a fixed pension

Consider a $3,000 monthly pension with no cost-of-living adjustment, and assume 2.5% average inflation. The payment never changes, so the entire effect shows up in what it buys. After 10 years it has the buying power of about $2,344 a month in today's terms. After 15 years it is about $2,071, after 20 years about $1,831, and after 25 years about $1,618 - a 46.1% reduction in real income over a retirement that many people actually live through.

Nothing went wrong in that scenario. The pension paid exactly what it promised every single month. This is why cost-of-living adjustments are worth so much, why long-dated fixed payments should be discounted before you compare them to anything, and why a retirement plan built only on nominal dollars tends to look better than it is.

Key terms explained

• Purchasing power: the quantity of real goods and services a fixed sum of money can buy. It falls when prices rise.
• Nominal dollars: the face value printed on the account statement, ignoring price changes.
• Real dollars (today's dollars): a future amount restated in current prices, which is what this calculator produces.
• Price multiplier: (1 + i)ⁿ, how many times more expensive the same basket becomes over the period.
• Consumer Price Index (CPI): the Bureau of Labor Statistics measure of the average price change for a representative basket of consumer goods and services.
• Real return: (1 + nominal return) ÷ (1 + inflation) − 1, the growth that remains after inflation is stripped out.
• Cost-of-living adjustment (COLA): a periodic increase in a payment intended to offset inflation. Social Security has one; most private fixed annuities do not.

What changes the result the most

Only three inputs exist, and they do not carry equal weight:

• The number of years is the strongest lever because the effect compounds. Going from 10 to 30 years at 3% moves the loss from 25.6% to 58.8%.
• The inflation rate is close behind and its influence grows with the horizon. Over 30 years, 2% costs you 44.8% of your value while 6% costs 82.6%.
• The amount changes the dollar figures proportionally but never changes the percentage. Doubling the amount doubles the loss in dollars and leaves the loss in percent untouched.
• Whether the money earns anything sits outside this calculator but dominates in real life. A balance earning the inflation rate holds its value exactly; anything less bleeds, anything more grows in real terms.

Tips for using the result well

• Run a range, not a point. Compute 2%, 3% and 5% and treat the spread as your planning band. A single rate implies a precision that inflation never delivers.
• Convert before you compare. Any choice between money now and money later should be settled in today's dollars on both sides.
• Check the real return, not the headline yield. At 4.5% nominal and 3% inflation the real return is about 1.46% a year, so $25,000 over 20 years grows to about $60,293 on paper but only about $33,383 in today's dollars.
• Watch the half-life. At 3% money loses half its buying power in about 23.4 years, at 4% in about 17.7 years, and at 6% in about 11.9 years. That single number reframes a long horizon quickly.
• Apply it to income too. A 2% raise in a 3% inflation year is a real pay cut of roughly 1%, and the same logic applies to rent, tuition and premiums.

Limitations and assumptions

• It assumes one constant average rate for the entire period. Real inflation moves every year, and a volatile path that averages 3% will not match a smooth 3% exactly.
• It assumes the money earns nothing. That is the correct assumption for cash and for a fixed payment, and a pessimistic one for an invested balance.
• It uses a general price level. Your personal inflation rate depends on your spending mix, and categories such as medical care, higher education and housing have historically moved differently from the overall index.
• It ignores taxes. Interest and gains are usually taxed in nominal terms, which makes the after-tax real return lower than the pre-tax one.
• It projects forward from an assumed rate rather than using published CPI history, because no index exists yet for future years.

How this compares to related calculators

Several tools on this site share the same arithmetic but answer different questions. Pick by what you are trying to decide:

• The Inflation Calculator leads with the future price of a purchase, so use it when you are asking what something will cost. This page leads with the real value of money you already hold, so use it when you are asking whether a sum will still be enough.
• The Compound Interest Calculator grows a balance at a return you choose; compare its result against the buying power figure here to see whether you are actually gaining ground.
• The Future Value Calculator projects a nominal future balance, which you can then divide by the price multiplier from this page to get it in today's dollars.
• The Rule of 72 Calculator gives the quick mental version: 72 divided by the rate approximates the doubling or halving time.
• The Savings Calculator and Retirement Calculator build the plan itself once you know the real target this page produces.

Sources

• U.S. Bureau of Labor Statistics - Consumer Price Index (CPI) home page, the official U.S. measure of consumer inflation.
• U.S. Bureau of Labor Statistics - CPI questions and answers, on how the index is built and what it covers.
• Board of Governors of the Federal Reserve System - Why does the Federal Reserve aim for inflation of 2 percent over the longer run?, the source of the 2% long-run target referenced above.