The full form of IRR is Internal Rate Of Return

Internal rate of return (IRR) is a method of calculating an investment’s rate of return. The term internal refers to the fact that the calculation excludes external factors, such as the risk-free rate, inflation, the cost of capital, or financial risk.

The method may be applied either ex-post or ex-ante. Applied ex-ante, the IRR is an estimate of a future annual rate of return. Applied ex-post, it measures the actual achieved investment return of a historical investment.

It is also called the discounted cash flow rate of return (DCFROR)

Return on investment—sometimes called the rate of return (ROR)—is the percentage increase or decrease in an investment over a set period. It is calculated by taking the difference between the current or expected value and the original value divided by the original value and multiplied by 100.