The real interest rate represents the true cost of borrowing or the real return on investment after removing the effect of inflation. In contrast, the nominal interest rate is the stated or market rate that includes inflation. The relationship between them is given by the Fisher equation:
(1 + nominal rate) = (1 + real rate) × (1 + inflation rate).
In simple terms, the real rate ≈ nominal rate – inflation rate. Real rates reflect actual purchasing power, while nominal rates show money growth. Understanding both helps investors and policymakers assess true returns, economic growth, and monetary policy effectiveness.