Finance & Accounting
Internal Rate of Return (IRR)とは何ですか？
定義
IRR is the discount rate that makes the net present value (NPV) of all cash flows from an investment equal to zero — in other words, the annualized return rate the investment is expected to generate. A project is worth pursuing if its IRR exceeds the hurdle rate or cost of capital.
IRR is calculated by solving for the rate r in: NPV = Σ [CF_t / (1+r)^t] = 0, where CF_t is cash flow in period t. Practically, IRR is solved iteratively (no closed-form solution). IRR is intuitive — it converts an investment's cash flow profile into a single annualized percentage return comparable to a bank interest rate. In real estate, private equity, and project finance, IRR is the primary performance metric. Common limitations: IRR assumes reinvestment at the IRR rate itself (often unrealistic for high-IRR projects), can produce multiple solutions with non-conventional cash flows, and can favor shorter-duration projects over higher-NPV longer-duration ones. Modified IRR (MIRR) addresses reinvestment rate issues. In venture capital, fund-level IRR (called 'net IRR' after fees and carry) is the standard performance benchmark reported to LPs.
なぜ重要か
IRR is the language of sophisticated investors — knowing your IRR (and its limitations) is essential for fundraising conversations, acquisition analysis, and capital project evaluation. A financial advisor or fractional CFO can build IRR models for your specific investment scenarios and help you understand whether your returns justify the capital and risk deployed.