Real Returns: Why Your 7% Is Actually 4% (and What That Costs)
The brokerage app says +7%. The grocery store says everything is 4% more expensive. The number that matters for your retirement is the difference, and it’s almost always smaller than the one you’re celebrating.
What “real return” actually means
Real return = nominal return adjusted for inflation. The exact formula:
real = (1 + nominal) / (1 + inflation) − 1A 7% nominal return with 3% inflation gives 3.88% real. People round to 4%. Close enough for back-of-envelope, but the formula matters when stakes are high.
The shortcut “subtract inflation from return” works at low rates and gets noticeably wrong at high rates. At 12% nominal and 8% inflation, the shortcut says 4%; the real number is 3.7%. A small error today, a measurable error at scale.
What the gap looks like over 30 years
We ran $100,000 through the calculator for 30 years, comparing what the brokerage will display vs what it can buy:
| Scenario | Nominal balance | Real purchasing power | The gap |
|---|---|---|---|
| 7% return, 0% inflation | $761,226 | $761,226 | $0 |
| 7% return, 2% inflation | $761,226 | $420,148 | −$341K |
| 7% return, 3% inflation | $761,226 | $313,679 | −$448K |
| 10% return, 3% inflation | $1,744,940 | $719,031 | −$1.0M |
That last row is what matters most. People hear “the stock market returns 10%” and plan around the $1.7M number. The number you can actually spend in 30 years is closer to $720K. Off by a factor of 2.4.
This isn’t a rounding error or a footnote. It’s the difference between “I retire comfortably” and “I keep working past 70.”
The 7% vs 10% confusion
When financial articles say “the stock market returns 7%,” they usually mean the real long-run S&P 500 return. When they say “10%,” they usually mean the nominal number. Both are correct; they’re describing the same data through different lenses.
The problem: most articles don’t say which one they mean. So someone reads “10% historical return,” uses that number in a retirement projection without subtracting inflation, and gets a number that’s silently 2-3× too optimistic.
Default rule: if a projection runs 30+ years and uses 10% returns without explicitly mentioning real-vs-nominal, assume the projection is wrong. Either rerun it at 7% real, or run it at 10% nominal with 3% inflation drag — both should give roughly the same real-dollar answer.
What the 1970s actually did to portfolios
US inflation averaged 7.4% from 1973-1982. The S&P 500’s nominal return over that decade was about 6.7%. Real return: negative 0.7% per year, for ten years.
A savings account paying 5% during that decade lost over 2% per year in real terms. Bonds did worse. The only assets that held up were commodities, real estate, and equities of companies with pricing power.
This is the historical case against “cash is safe.” Cash preserves the number. Inflation eats the value behind the number. Both facts are simultaneously true, and “safe” depends entirely on which one you care about.
What to do about it
Three things, in order of payoff:
- Project in real terms. Always. Use real return rates (4-5% for diversified equities, 1-2% for bonds, ~0% for cash) when planning, not nominal rates. The number you arrive at is the number you can spend.
- Own assets that compound faster than inflation. Diversified equities, real estate, possibly TIPS for the bond portion. Avoid being heavy in long-duration nominal bonds or excess cash.
- **Reread “high yield” as “yield.” A 4% savings account during 3% inflation is a 1% account. Looks like 4× the alternative; really 1× the alternative.
What this assumes
This whole framework assumes inflation runs at a predictable long-run average. Reality is lumpier:
- Inflation regimes shift. The post-1980 era of 2-3% inflation is a regime, not a guarantee. The 1970s happened. Either could happen again.
- Personal inflation differs from CPI. If your spending is heavy on healthcare, education, or housing, your personal inflation rate may run 1-2% higher than headline CPI. Plan accordingly.
- Average ≠ sequence. Hitting 7% real on average over 30 years doesn’t mean smooth returns. The sequence of good and bad years matters enormously, especially near retirement (sequence-of-returns risk).
The calculator shows both
That’s the whole point of the inflation toggle in the Compound Interest Calculator. You see the impressive nominal number and the realistic real number side by side. The gap between them is what you should be planning around.
Default it to 7% return / 2.5% inflation and start from there. Adjust both based on your actual asset mix and your honest read of where inflation is heading.