Definition
The real interest rate is the interest rate that remains after removing the effect of expected inflation, expressing the rate of return in terms of purchasing power rather than dollar amounts.
Why it matters
Real interest rates are what actually matter for long-horizon financial decisions, because they describe what a saver's money will be able to buy in the future rather than what it will be denominated in. Lifetime income calculations rest on a real-rate assumption — the discount rate used to value future income flows is a real rate when the goal is to preserve real purchasing power over decades. Confusing nominal and real rates is one of the most consequential errors in retirement income reasoning.
How it works
The real interest rate is computed as the nominal interest rate minus the expected inflation rate, with the resulting figure representing the return after the loss in purchasing power has been removed. For example, a savings account paying a 4% nominal annual interest rate during a period when inflation is expected to run at 2% delivers a real return of approximately 2%. The relationship is approximate at low rates and exact under a compounded formulation, but the intuition is the same: real rates measure return in purchasing power. Real rates can be negative, and persistently negative real rates were a defining feature of the 2009 to 2022 period in the United States. Treasury Inflation-Protected Securities yields are a market-implied real rate observable directly without needing to subtract an inflation expectation; the difference between Treasury yields and TIPS yields of the same maturity is the breakeven inflation rate.
In practice
For an individual planning retirement income, the practical question is what real rate to assume for the savings being projected forward and for the income being valued in today's dollars. Conservative planning typically uses a low real rate — frequently zero to two percent — for the savings component, reflecting the risk that nominal returns will not significantly exceed inflation over the planning horizon. Quoted annuity payout rates and bond yields are nominal; the same nominal rate buys more lifetime real income when expected inflation is low than when expected inflation is high. A professional working with retirement income projections should be explicit about whether a quoted rate is nominal or real, and any income figure expressed in today's dollars implicitly assumes a real-rate framing.
In the Longevity Standard Framework
Real interest rate is the structural mechanism underlying the Longevity Standard framework's cost-of-income calculation. The realized value metric, measured as the market-based uplift over solo drawdown divided by the theoretical uplift over solo drawdown, is also expressed in real terms. Shifts in the prevailing real rate environment move the cost of income for every arrangement, with the same shift simultaneously affecting solo drawdown, the frictionless benchmark, and asset-backed insurer products.
Related terms
- Nominal interest rate
- Cost of income
- Realized value
- Discount rate
- Real versus nominal discount rate
- Inflation risk
- Breakeven inflation rate
- TIPS