IRR Calculator
以下详细说明暂以英文提供。
What IRR tells you
The internal rate of return is the annualized efficiency of an investment: the rate r that makes the present value of the money you receive equal the money you put in:
0 = −Investment + CF₁/(1+r) + CF₂/(1+r)² + …
There is no closed-form solution for most cash flow patterns, so this calculator solves it numerically by bisection: it narrows a bracket of rates until the NPV crosses zero to within 1e−7. Use IRR to compare projects of different lengths on a common percentage scale.
常见问题
What does it mean when IRR cannot be found?
Bisection needs the NPV to change sign across the search range. If the cash flows never repay the initial investment, the NPV is negative at every rate tested and no meaningful IRR exists — the money simply never comes back.
IRR or ROI — which should I use?
ROI ignores time: doubling your money in 1 year and in 20 years both show 100%. IRR annualizes, so the 1-year case shows about 100% and the 20-year case about 3.5%, making it better for comparing investments over different periods.