Why Your Real Return Is Not Your Nominal Return
Inflation and taxes both quietly erode a headline investment return — here's the exact math behind each, and why a positive nominal return can still be a real loss.
Published July 13, 2026
A nominal return — the headline number quoted on any account statement — measures growth in raw currency terms. Two separate forces quietly reduce what that number is actually worth in real terms: inflation, and taxes.
Inflation: the Fisher equation, exactly
rreal = (1 + rnominal) ÷ (1 + i) − 1
The exact relationship, named for economist Irving Fisher — not the common "nominal minus inflation" shortcut.
The Real Rate of Return Calculator shows the exact break-even case: when nominal return equals inflation, real return is exactly zero — the investment merely preserved purchasing power rather than growing it. According to U.S. Bureau of Labor Statistics data, inflation has varied substantially across different periods, which is exactly why a single nominal return figure can mean very different things depending on when it was earned.
Taxes are typically owed on the nominal gain, not the smaller real gain — meaning an investment with a modest real return can still generate a tax bill calculated on a larger nominal figure, pushing the after-tax real return lower still.
Taxes: the second erosion
| Account type | 25-year balance ($10K + $500/mo, 8% gross) |
|---|---|
| Tax-advantaged | $548,914.96 |
| Taxable (1.5% annual tax drag) | $424,980.24 |
The Taxable vs. Tax-Advantaged Account Calculator shows $123,934.72 lost to ongoing annual tax drag over 25 years — and that’s before inflation is even applied on top.
Putting both together
Neither erosion is visible on an account statement showing a rising nominal balance, which is exactly what makes both easy to underweight. A “safe” bond or savings account paying what sounds like a solid nominal rate can represent a real loss once inflation is applied, and the situation can get materially worse in a taxable account where tax is owed on the (larger) nominal gain rather than the real one. For adjusting a specific savings goal expressed in today’s dollars, the Inflation Calculator converts a future nominal target into what it’s actually worth in today’s purchasing power.
Related calculators
Real Rate of Return Calculator
Find out what an investment's return is actually worth after inflation — the number that determines whether your money's real purchasing power grew at all.
Taxable vs. Tax-Advantaged Account Calculator
See exactly how much annual tax drag costs a growing investment over decades — the specific advantage a 401(k), IRA, or similar tax-advantaged account has over an ordinary taxable brokerage account.
Inflation Calculator
See what today's money will be worth in the future after inflation — and understand why a fixed sum feels smaller and smaller the longer it sits unused.