What is the Difference Between Real and Nominal Return?

By EC Assets Research Team · Published 17 August 2026 · Updated 17 August 2026

Real vs Nominal Return: Nominal return is what an investment pays in currency units; real return is what it pays in purchasing power. The two are linked multiplicatively rather than by subtraction, and because tax is levied on the nominal figure, a positive nominal return after tax can still be a real loss.

What Real Return Actually Measures

A nominal return states how many more currency units an investor holds at the end of a period. A real return states how much more the investor can buy. The gap between them is inflation, and over long horizons it is usually the larger of the two effects on wealth.

The distinction is not presentational. Almost every headline investment figure — coupon rates, index returns, fund factsheets, expected-return assumptions — is nominal, while almost every objective an institution actually has is real: a pension paying benefits linked to earnings, an endowment supporting a spending programme, a family office preserving purchasing power across generations. The translation between the two languages is where mandates are met or missed.

How It Works

The relationship is multiplicative. One unit of purchasing power grows by the nominal return and shrinks by inflation, so the two compound against each other:

$$1 + r_{\text{real}} = \frac{1 + r_{\text{nominal}}}{1 + i}$$

Rearranged, this is the Fisher equation:

$$r_{\text{real}} = \frac{1 + r_{\text{nominal}}}{1 + i} - 1$$

The familiar shortcut subtracts instead:

$$r_{\text{real}} \approx r_{\text{nominal}} - i$$

The approximation is adequate when both figures are small and diverges as either grows. At 5 percent nominal and 3 percent inflation, subtraction gives 2.00 percent against an exact 1.94 percent — a difference of six basis points. At 20 percent nominal and 15 percent inflation, subtraction gives 5.00 percent against an exact 4.35 percent, an error of 65 basis points that compounds every year it is repeated.

Purchasing power remaining, by inflation rate and horizon

Purchasing power of one currency unit held in cash, computed as the reciprocal of cumulative inflation. At 3 percent — an unremarkable rate — money loses nearly 45 percent of its value across a twenty-year mandate.

Worked Example

A portfolio returns 5 percent in a year in which inflation runs at 3 percent. The exact real return is:

$$\frac{1.05}{1.03} - 1 = 1.94%$$

Now introduce tax, which is levied on the nominal figure. At a 30 percent rate, the nominal return net of tax is 3.5 percent, and the real return becomes:

$$\frac{1.035}{1.03} - 1 = 0.49%$$

The investor earned 5 percent, paid tax on all of it, and advanced purchasing power by less than half a percentage point. This is the mechanism sometimes described as an inflation tax: because the tax base is nominal, inflation raises the effective rate on real gains without any change in tax law.

One 5 percent nominal return, four inflation environments

At 5 percent inflation the nominal return exactly preserves purchasing power before tax and destroys it after tax. The break-even nominal return rises faster than inflation once tax is applied.

When It Applies (and Limitations)

Which price index. Real return depends on the deflator chosen, and no single index describes every investor. A published CPI weights a national consumption basket; an endowment funding salaries and construction faces a different one; a retiree with concentrated healthcare and housing costs faces another. Institutions with genuinely idiosyncratic cost bases sometimes construct bespoke deflators, and the choice materially changes whether a mandate is being met.

Inflation is measured with a lag and revised. The real return of a period is not known when the period ends. Index-linked instruments handle this with an explicit indexation lag, which introduces a small basis between the instrument and contemporaneous inflation.

Expected versus realised. Market-implied inflation — the gap between nominal and index-linked yields of the same maturity — is a break-even, not a forecast. It contains an inflation risk premium and liquidity effects, so the ex-ante real yield is not simply the ex-post real return.

Deflation inverts the arithmetic. With negative inflation the same formula produces a real return above the nominal one. Cash then earns a positive real return without any credit or duration exposure, which is why deflationary regimes are so hostile to risk-asset valuations.

Currency. For an unhedged foreign holding, the relevant inflation is that of the investor's own consumption basket, not the asset's home market. Exchange-rate movements partially offset inflation differentials over long horizons and reliably fail to do so over short ones.

Why It Matters for Institutional Investors

Liability-driven investing. Pension liabilities linked to prices or earnings are real obligations. Matching them with nominal bonds leaves an unhedged inflation exposure that only reveals itself when inflation surprises, as it did across 2021 and 2022 for schemes holding nominal duration against indexed benefits.

Spending rules. An endowment distributing 4 percent a year and intending to preserve purchasing power in perpetuity requires a 4 percent real return plus costs, not a 4 percent nominal one. Stated in nominal terms during a 3 percent inflation regime, the required return is above 7 percent — a materially different portfolio.

The safety of cash. Cash carries no mark-to-market volatility and is not therefore riskless in real terms. A deposit yielding 4 percent while inflation runs at 6 percent loses 1.9 percent of purchasing power a year with perfect certainty. Volatility and risk part company most visibly here.

Index-linked bonds. Inflation-linked government debt pays a contractual real yield, making it the only instrument whose real return is known at purchase and held to maturity. That is also why its quoted yields look unimpressive next to nominal debt: they are already the real number.

Long-horizon assumptions. Capital-market assumptions compounded across decades are extremely sensitive to whether they were stated in real or nominal terms. Mixing the two — a real return assumption applied to a nominal liability, or vice versa — is among the most common and least visible errors in strategic asset allocation.

References

1. Fisher, I. (1930). The Theory of Interest. Macmillan.
2. Bodie, Z., Kane, A., & Marcus, A. J. (2021). Investments (12th ed.). McGraw-Hill.
3. Bank of England. Inflation and the 2% Target. (https://www.bankofengland.co.uk/monetary-policy/inflation)
4. UK Debt Management Office. Index-linked Gilts. (https://www.dmo.gov.uk)