A nominal interest rate is the rate you see quoted on a loan, savings account, or government bill — “5% a year.” A real interest rate subtracts inflation to approximate the change in purchasing power. If you earn 5% nominally while prices rise 3%, your approximate real return is 2%. That gap is why macroeconomists obsess over real rates when judging how tight or loose financial conditions really are.

The Fisher idea in plain language

Irving Fisher’s insight is that nominal rates embody a real return plus expected inflation (and risk premia). A common classroom approximation is:

real rate ≈ nominal rate − inflation rate

For precision, especially when inflation is high, use the multiplicative form: (1 + nominal) / (1 + inflation) − 1. For everyday intuition at moderate inflation, the subtraction shortcut is usually enough.

Which inflation? Past inflation (ex post real rates) answers “what did I actually earn after prices moved?” Expected inflation (ex ante real rates) answers “what real return do I think I am bargaining for?” Policy and investment decisions are mostly about the ex ante concept, even though expectations are hard to observe.

Why real rates matter more than headlines

Suppose Bank Rate or the federal funds rate rises by two percentage points, but expected inflation rises by the same amount. The real policy stance may be little changed. Conversely, if nominal rates stay put while inflation falls, real rates rise and conditions tighten without a single headline hike.

Try the intuition. The site’s inflation adjuster shows how a fixed cash amount loses purchasing power over time — the same logic that turns nominal interest into real interest.

Households feel real rates through mortgage and rent costs relative to wage growth, and through the real return on cash and bonds. Firms care about the real cost of capital versus expected real revenues. Governments care about the real burden of debt service relative to tax bases that also move with inflation and growth.

Neutral or natural real rates

Central bankers often talk about a neutral real rate (sometimes r*) — a level consistent with inflation near target and the economy at potential, abstracting from shocks. If the real policy rate sits well above neutral, policy is restrictive; well below, accommodative. Estimates of r* are uncertain and move slowly with productivity, demographics, and global saving–investment balances.

A higher nominal rate is not automatically “tight” if inflation and inflation expectations are higher still.

Measuring real rates in the wild

Useful observables include:

  • Policy rate minus a core or expected inflation measure
  • Inflation-indexed bond yields (TIPS in the US; index-linked gilts in the UK), which embed market-implied real rates over specific horizons
  • Survey measures of inflation expectations from households, firms, or professionals

Indexed-bond yields are powerful but not pure: liquidity premia, inflation risk premia, and technical factors matter. Still, they are among the best market summaries of medium-term real rate views.

Example (illustrative)

If a one-year deposit pays 4% and expected CPI inflation is 2%, the approximate ex ante real return is 2%. If inflation surprises at 5%, the ex post real return is about −1%. Neither figure is investment advice; they are arithmetic illustrations.

UK and US lenses

UK readers often compare Bank Rate with CPI or CPIH inflation and watch index-linked gilt real yields. US readers compare the federal funds rate with PCE or CPI inflation and watch TIPS real yields on FRED. Cross-country comparisons should note different inflation baskets and indexation conventions.

Continue with inflation, monetary and fiscal policy, quantitative easing, and glossary real interest rate.

Short rates, long rates, and curves

Policy rates are overnight or very short-term. Households and firms often borrow at longer maturities. The real policy rate can move while longer real yields move less — or more — depending on growth expectations, term premia, and quantitative tightening or easing. Looking only at the overnight real rate can therefore misstate the cost of a 30-year mortgage or a corporate bond.

Yield curves encode expectations of future short rates plus risk premia. When inflation expectations fall, nominal yields may fall even if real yields hold steady. Breaking a move into real and inflation-compensation pieces (via indexed bonds or inflation swaps) is a standard way professionals avoid mixing those stories.

Savers, borrowers, and the inflation tax on cash

Cash and non-interest current accounts earn a nominal rate near zero in many periods. Their real return is approximately minus inflation: an inflation tax on idle balances. Term deposits and bonds may compensate, but only if their nominal yields clear expected inflation and credit risk. This is why periods of negative ex post real policy rates feel painful for risk-averse savers even when headline rates look “normal” relative to history.

Borrowers with fixed nominal debts gain when inflation surprises to the upside, because repayments are cheaper in goods terms — unless their incomes fail to keep up or their rates reset quickly. Floating-rate UK mortgages can transmit Bank Rate into real household burdens faster than many long-fixed US mortgages. That institutional detail belongs in any UK–US comparison of living with real rates.

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