Inflation-Adjusted Return Calculator

Year by year

The nominal column is your account statement. The real column is the same balance expressed in the buying power of money today.

Year	Nominal value	Value in today's money	Price level

The formula, and why subtraction is not quite right

Almost everyone estimates a real return by subtracting inflation from the nominal return. It is close, and it is wrong in a way that grows with the size of the numbers. The exact relationship is the Fisher equation:

Real return = (1 + nominal) / (1 + inflation) - 1

With the default inputs of a 7% nominal return and 3% inflation, that is 1.07 / 1.03 - 1 = 0.038835, so 3.88%. The subtraction shortcut says 4.00%. The 0.12 percentage point gap looks trivial for one year. Over 20 years it compounds into a difference of several hundred dollars on a $10,000 balance, and the gap widens sharply when either rate is high. In a 20% nominal, 15% inflation environment the shortcut is out by two thirds of a percentage point.

A worked example with the defaults

Put $10,000 to work at 7% a year for 20 years while prices rise 3% a year:

• Nominal ending value: $10,000 x 1.07^20 = $38,696.84.
• Prices over the same 20 years: 1.03^20 = 1.8061, so the cost of living is 80.6% higher.
• Ending value in today's money: $38,696.84 / 1.8061 = $21,425.50.
• The same answer from the real rate: $10,000 x 1.038835^20 = $21,425.50.

Your statement shows you nearly quadrupled the money. In terms of what it buys, you slightly more than doubled it. Both facts are true at once, and only the second one pays for anything.

Where the real number changes decisions

Nominal thinking makes cash and short-term bonds look safer than they are. Through much of the 1970s, savers earning high headline interest rates lost purchasing power every year because inflation ran higher still. The reverse also happens: an era of low nominal rates with low inflation can deliver a perfectly decent real return. What the CPI release measures, and how markets read it, is covered in inflation and CPI explained.

Retirement planning is where this bites hardest, because the horizon is long enough for a two point difference in assumed inflation to change the answer entirely. A 30-year plan built on nominal returns will overstate what the money supports. Build it in real terms instead, as described in retirement portfolio basics.

What to do about it

Treasury Inflation-Protected Securities adjust their principal with the CPI, which makes their quoted yield a real yield directly. They are described alongside bills, notes and bonds in the Treasury securities guide. For a nominal bond, compare its yield to maturity from the bond yield calculator against your inflation assumption to see whether the income survives contact with prices.

If you want the compound growth rate behind a past result before adjusting it, start with the stock return and CAGR calculator, then bring it back here. To see how much longer money takes to double in real terms, feed the real return into the Rule of 72 calculator.