Nominal vs. real returns: what inflation quietly takes
Your investment can grow on paper while buying you less. Here's how to see the difference — and why we always show 'today's dollars'.
A nominal return is the headline number — the raw growth in dollars. A real return is what's left after you subtract inflation: the growth in actual purchasing power. They can tell very different stories, and the gap is the single most under-appreciated force in long-term investing.
A dollar isn't a fixed thing
Prices drift up over time. A basket of goods that cost $1.00 in 2010 might cost around $1.40 today, which means a 2010 dollar and a 2026 dollar simply aren't the same unit of value. So when an old investment "tripled," part of that tripling was just the dollar shrinking underneath it. Comparing a result across many years without adjusting for inflation is like measuring a journey with a ruler that keeps getting shorter.
How the adjustment works
Economists track the price level with the Consumer Price Index (CPI). To express a future amount in today's dollars, you scale by the ratio of the price index then versus now:
real value = nominal value × (CPI at start ÷ CPI at end)
That deflates the headline figure back to what it would actually buy in start-year terms. It's why every result here shows both numbers — the eye-catching nominal value and the sober real one. The honest gap between them is the cost of time itself.
Why it matters more than people think
Over short stretches inflation is a rounding error. Over decades it's decisive: a few percent a year compounds into roughly halving the dollar's purchasing power every couple of decades. An investment that "beat the market" but barely outran inflation didn't make you much richer in any way you can spend. This is also the case for investing in the first place: cash left under the mattress quietly loses ground every year, so the real question is never "did it grow?" but "did it grow faster than prices?"
See it for yourself. Any scenario shows the inflation-adjusted result next to the nominal one — try the S&P 500 since 2005 — and the methodology page documents the exact CPI source and adjustment.