About the IRR Calculator
An IRR (Internal Rate of Return) calculator computes the discount rate at which the net present value of a stream of cash flows equals zero — effectively, the annualized return on an investment with irregular inflows and outflows. IRR is the standard metric for evaluating real estate, private equity, capital projects, and any investment where money goes in and comes out at irregular intervals. It handles complexity that simpler measures like ROI can't.
When IRR is the right tool
IRR shines when cash flows are irregular: a real estate investment with an upfront purchase, monthly rents over years, periodic capital expenditures, and a sale at the end. ROI alone can't compare such an investment to a simpler one; CAGR doesn't capture the operating cash flows. IRR aggregates them all into a single annualized rate.
For startup investments, IRR captures the relationship between an upfront capital infusion and a later exit (sale, IPO). For private equity and venture capital, IRR is the headline metric (often quoted as "3.5× MOIC at 22% IRR over 7 years" — multiple-on-invested-capital plus IRR plus duration).
Why IRR is computed iteratively
IRR is the rate that satisfies: 0 = Σ Cash flow_t / (1 + r)^t. Unlike future-value problems, this equation has no closed-form solution — there's no algebraic way to isolate r. Calculators solve iteratively (Newton's method, bisection, etc.), starting from a guess and refining until NPV converges to zero.
Most spreadsheet IRR functions converge in milliseconds for typical cash flow patterns. Pathological cases (cash flows that switch sign multiple times) can have multiple IRRs or no real IRR at all — a sign that IRR may not be the right metric for that specific situation.
Common IRR pitfalls
Reinvestment assumption: IRR implicitly assumes intermediate cash flows are reinvested at the IRR rate itself. For a project with an unusually high IRR, this assumption is unrealistic — there's typically nowhere else to earn the same rate. Modified IRR (MIRR) addresses this by separating the reinvestment rate from the financing rate; for high-IRR projects, MIRR is often substantially below IRR.
Multiple sign changes: when cash flows cross zero more than once (e.g., investment, profit, more investment, sale), the IRR equation can have multiple roots. Calculators may report whichever they find first, which may not be the economically meaningful one. NPV plus a cost of capital is more reliable in these cases.
Comparison across different scales: an investment with $10,000 in and IRR 30% is not necessarily better than $1,000,000 in and IRR 12%. IRR doesn't reflect investment size, only rate of return. NPV captures total dollar value created.
IRR in real estate and private equity
Real estate IRR typically blends operating cash flows (net rental income after expenses) with terminal value (sale price net of selling costs). A residential rental with 6% cap rate, modest leverage, and 3% annual appreciation often produces leveraged IRR in the 12–18% range over 5–10 year holds — meaningfully above unlevered S&P returns at typical leverage.
Private equity quotes IRR alongside MOIC (multiple on invested capital) because the two together describe both the rate and total magnitude of returns. A 25% IRR over 4 years is mathematically equivalent to MOIC of ~2.4×; a 25% IRR over 7 years is ~4.8×. The duration matters for capital deployment cycles even when the IRR is identical.
Formula
- CF_t = Cash flow at time t (positive = inflow, negative = outflow)
- t = Time period (typically years; can be any consistent interval)
- IRR = The rate that makes NPV equal zero
Worked examples
Real estate investment
Year 0: −$200,000 (purchase + closing). Years 1–5: +$15,000/year (net rental income). Year 5: +$60,000 (sale net of costs, in addition to year-5 rent). IRR ≈ 8.3%. The same cash flows annualized via simple ROI: total return ($75,000 + $60,000 − $200,000) = -$65,000 — but with positive operating returns it's actually a winning investment when properly time-discounted.
Startup investment
Year 0: −$50,000 invested. Year 7: +$300,000 from acquisition. IRR = (300/50)^(1/7) − 1 ≈ 29%. MOIC: 6×. Both numbers describe the same return; investors typically use both because each captures a different dimension.
Multi-period business with negative interim cash flow
Year 0: −$100,000. Year 1: −$50,000 (further investment). Years 2–5: +$30,000/year (positive cash flow). Year 5: +$200,000 (terminal value, in addition to year 5 cash flow). IRR ≈ 18%. The single rate captures the irregular cash flow pattern — ROI alone can't.
Frequently asked questions
What's a good IRR?
Depends on the investment type and risk. For stable real estate: 8–12% leveraged. For venture capital: target 25%+ to compensate for the high failure rate. For corporate capital projects: typically targeted at the company's cost of capital plus a margin (so a firm with 8% WACC might require 12%+ IRR on new projects).
What's the difference between IRR and ROI?
ROI is a single-period total return: gain divided by initial cost. IRR handles multiple, irregular cash flows by finding the rate that makes their net present value zero. For investments with cash flows over time, IRR is more accurate; for one-shot investments, the two converge to the same number.
What's the difference between IRR and CAGR?
CAGR assumes a single starting point and ending point with no intermediate cash flows. IRR handles intermediate cash flows directly. For an investment with no intermediate inflows or outflows, IRR equals CAGR. Otherwise, IRR captures the timing pattern that CAGR misses.
Why does IRR sometimes give weird numbers?
Most commonly: cash flows that cross zero multiple times can produce multiple IRRs or no real IRR. The implicit reinvestment-at-IRR assumption is unrealistic for very high IRRs. For these cases, NPV at an explicit cost of capital is often more meaningful than IRR.
Should I use IRR or NPV?
Both, when possible. NPV directly measures dollar value created at a specified cost of capital. IRR gives a rate, which is intuitive for comparison. NPV is more rigorous for capital allocation decisions; IRR is more intuitive for communication. Most professional evaluations report both alongside payback period and sensitivity analysis.
What's MIRR?
Modified Internal Rate of Return. It addresses the implicit IRR assumption that intermediate cash flows are reinvested at the IRR rate, which is unrealistic for high-IRR projects. MIRR uses a separate reinvestment rate (typically the cost of capital) and financing rate. For high-IRR projects, MIRR is typically substantially below IRR — and arguably more honest.
Related calculators
Concepts
Sources & methodology
- CFA Institute — IRR and capital budgeting — source