Understanding your real investment returns

The number on your statement is lying

When you log into your investment account and see your balance, you’re looking at a nominal number. It tells you how many dollars (or pounds, or euros) the account holds today. What it doesn’t tell you is what those dollars can actually buy.

Inflation works in the background, quietly raising the cost of everything from groceries to rent to healthcare. Every percent of inflation reduces what each dollar in your account is worth — and over decades, the effect is dramatic. A retirement projection that shows $1 million in 30 years sounds impressive, but at 3% inflation that $1 million has the purchasing power of about $412,000 in today’s money. Half the headline figure has been absorbed by inflation before you’ve spent a cent.

This gap between the nominal number and the real value is one of the most consistently underestimated forces in personal finance. Once you start seeing investments through both lenses, your sense of “how much do I actually have?” changes permanently.

Nominal vs real: a small word, a huge consequence

A nominal return is the percentage growth your investment shows on paper — the rate the brokerage statement reports. A real return is that same growth adjusted for inflation. The two are related by a simple but powerful formula:

Real return = ((1 + nominal) / (1 + inflation) − 1) × 100

For practical purposes at low inflation rates, the shortcut real ≈ nominal − inflation works well. So a 7% nominal return with 3% inflation is roughly a 4% real return. A 5% nominal return with 4% inflation is barely 1% real. And a 3% nominal return with 4% inflation is negative in real terms — your money is losing purchasing power even as your balance technically grows.

Why even a small inflation rate compounds dramatically

The real story emerges over long horizons. At 3% inflation, prices double every ~24 years. At 5%, they double every ~14 years. At 10% — a level seen during inflationary shocks — prices double every ~7 years. The same $100 worth of groceries today costs $200 of nominal dollars to buy in two doublings, regardless of what an investment account has done in the meantime.

For a 30-year retirement projection at 3% inflation, the cumulative price-level increase is about 142%. A $1,000 monthly withdrawal at retirement provides only as much real spending power as $412 today. This is why financial planners insist on projecting in real terms — nominal numbers always feel reassuring and always overstate the lifestyle they support.

The historical gap

Long-run nominal stock-market returns have historically averaged around 8%–10% in developed markets. Long-run inflation has averaged 2%–4% in the same economies. So the long-run real equity return — the actual growth in purchasing power — is typically 5%–7%, not 8%–10%. That’s a meaningful difference once you compound it over a career.

This is the figure most academic studies and prudent financial planners quote when they discuss long-term returns. When a piece of investment marketing says “stocks return 10% a year,” they mean nominal — the inflation-adjusted truth is a few percentage points lower.

How real return changes investment decisions

Once you start thinking in real terms, several things shift:

• Cash savings look much less safe. A 2% savings account at 3% inflation is losing real value at 1% per year. The “safety” of cash is measured against nominal balances; in real terms, idle cash is decaying.
• Long-horizon projections become more conservative. A 25-year-old planning for retirement should run their numbers at 5% real, not 8% nominal. Same money, far more honest expectation.
• Withdrawal rates become more cautious. The classic “4% safe withdrawal rate” is a real-terms figure — it means 4% adjusted for inflation each year, not 4% of the nominal balance.
• Bond yields look different. A bond yielding 4% in a 4% inflation environment isn’t returning anything in real terms. The same bond in a 1% inflation environment is producing a healthy 3% real return.

What inflation assumption to use

For long-horizon planning, 2.5%–3% is the typical assumption — it sits at or just above the long-term central-bank targets in most developed economies. Some periods (the 1970s, the early 2020s) have run materially higher. Some periods (the 2010s) have run materially lower.

The honest approach is to model multiple scenarios — a base case at 3%, a higher-inflation stress case at 5%, and a low-inflation case at 1.5%. The differences over 30 years are dramatic, and they tell you how robust your plan is to surprises.

A practical reframe

Try this exercise: take any nominal figure from a long-horizon projection and divide it by (1 + inflation)^years. The result is what that future amount is worth in today’s purchasing power. A $2 million projection in 40 years at 3% inflation is worth about $613,000 in today’s dollars — still substantial, but a far cry from “$2 million in retirement”. This single reframe is the difference between feeling overconfident in your numbers and planning realistically.

Use the calculators together

Start with our real return calculator to see the side-by-side nominal-vs-real projection — including the year-by-year inflation erosion that quietly widens the gap. Then run our compound interest calculator at the real rate of return rather than the nominal rate; the projection will look smaller, but it will be much closer to what you can actually buy with the result.