MIRR Calculator

The Modified Internal Rate of Return (MIRR) is a capital budgeting metric that addresses well-documented shortcomings of the traditional Internal Rate of Return (IRR). While IRR implicitly assumes that every positive cash flow generated by a project is reinvested at the same rate as the IRR itself — an assumption that is rarely realistic in practice — MIRR uses two explicitly stated, separate rates: a finance rate (the cost of capital used to fund the project) and a reinvestment rate (the expected return on reinvested cash flows).

Because these two rates reflect actual market conditions rather than a mathematical artifact, the MIRR calculator produces a more conservative and credible estimate of a project's true profitability. Analysts, CFOs, and investment managers widely prefer MIRR when evaluating capital projects, acquisitions, real estate developments, and any multi-year investment with irregular cash flows.

A higher MIRR indicates a more attractive investment relative to the cost of capital. As a general decision rule, a project is worth pursuing when its MIRR exceeds the hurdle rate (the minimum required rate of return). When comparing mutually exclusive projects of the same duration, the project with the higher MIRR is typically preferred. Because MIRR always produces a single, unique answer — unlike IRR, which can yield multiple solutions for unconventional cash flow streams — it is considered a more robust tool for ranking competing investments.

This MIRR calculator lets you enter an initial investment, up to any number of annual cash flows (positive or negative), a finance rate, and a reinvestment rate. It instantly displays your MIRR alongside the traditional IRR so you can see exactly how the two metrics differ for your specific project.

The MIRR formula combines two present/future value calculations into a single compounded growth rate over the life of the project. Understanding each component helps you select appropriate rate assumptions and interpret the result correctly.

The calculator separates cash flows into two groups. All negative cash flows (outflows, including the initial investment) are discounted back to time zero using the finance rate to produce a single present value of costs (PV of negatives). All positive cash flows (inflows) are compounded forward to the end of the project using the reinvestment rate to produce a single terminal value (FV of positives). MIRR is then the nth-root of the ratio of these two numbers, minus one.

In the calculator implementation, the initial investment is always treated as a negative outflow added directly to the PV of negatives. Each periodic cash flow is examined: positive flows are compounded to the terminal period using CF x (1 + r_reinvest)^(n - i - 1), while negative flows are discounted to period zero using |CF| / (1 + r_finance)^(i + 1). The final MIRR is computed as (FV_positives / PV_negatives)^(1/n) - 1.

Traditional IRR has two fundamental flaws that MIRR corrects. First, IRR assumes that every interim cash flow is reinvested at the IRR itself. If a project produces a 30% IRR but the firm's typical reinvestment opportunities only return 10%, the actual realized return will be far lower than 30%. MIRR forces the analyst to declare an explicit reinvestment rate, producing a more grounded figure.

Second, IRR can produce multiple solutions — or no real solution at all — when a project has non-conventional cash flows (cash flows that change sign more than once, such as a mining project with large reclamation costs at the end). MIRR always produces exactly one answer because the mathematical structure of the formula involves a single positive ratio raised to a fractional exponent.

The MIRR calculator on this page also computes the traditional IRR using Newton-Raphson iteration so you can compare both metrics side by side. The IRR vs MIRR difference result card tells you instantly how optimistic or pessimistic the IRR is relative to the more realistic MIRR. In most cases, when the reinvestment rate is lower than the IRR, MIRR will be lower than IRR — reflecting the drag of reinvesting at a more modest rate.

For capital budgeting decisions — especially when ranking multiple competing projects — finance professionals, corporate treasurers, and investment analysts consistently recommend supplementing IRR analysis with MIRR to avoid overstating a project's attractiveness.

Selecting appropriate rate inputs is the most judgment-intensive part of any MIRR calculation. The rates you choose directly determine how conservative or aggressive your return estimate is.

Finance Rate (Cost of Capital): This is the rate at which the firm borrows money or the opportunity cost of the capital deployed in the project. A natural choice is the company's Weighted Average Cost of Capital (WACC), which blends the after-tax cost of debt and the cost of equity weighted by capital structure. For leveraged buyouts or project finance deals, analysts sometimes use the project-specific cost of debt. If you are an individual investor evaluating a real estate deal, your mortgage rate or margin loan rate may be the appropriate finance rate.

Reinvestment Rate: This is the rate you expect to earn on cash flows once you receive them. Common benchmarks include the firm's WACC, a long-term treasury bond yield (a conservative assumption), a money market rate, or the expected return of a diversified equity portfolio. Using a lower reinvestment rate is more conservative and produces a lower MIRR; using a higher rate is more optimistic. Many practitioners set the reinvestment rate equal to the finance rate for simplicity, though this need not be the case.

Both rates should reflect realistic, achievable figures based on your specific circumstances — not inflated assumptions designed to make a marginal project look attractive. MIRR's value is precisely that it forces you to be explicit and realistic about these assumptions rather than letting the math assume them for you.

MIRR is especially useful in several common investment analysis scenarios. In corporate capital budgeting, finance teams use MIRR alongside NPV to evaluate equipment purchases, plant expansions, R&D projects, and acquisitions. MIRR provides a percentage return easy to communicate to stakeholders, while NPV provides the absolute dollar value created.

In real estate investment analysis, MIRR is frequently used to evaluate development projects, commercial property acquisitions, and REIT investment decisions. Real estate cash flows often have large upfront construction costs followed by operating inflows and potentially large costs at disposition — exactly the non-conventional cash flow pattern where traditional IRR is least reliable.

Private equity and venture capital analysts sometimes use MIRR to adjust for the fact that early-stage distributions must be reinvested in new deals at a rate that may differ substantially from the fund's IRR. MIRR provides a reality check on the fund's advertised return figure.

In project finance for infrastructure, energy, and mining, MIRR is used to handle terminal reclamation or decommissioning costs that create sign changes in the cash flow stream. MIRR cleanly handles these scenarios without producing spurious multiple IRR solutions.

The MIRR calculator is also useful for individual investors evaluating rental properties, small business investments, or any multi-year investment where they want to be realistic about how they will deploy interim cash flows rather than assuming reinvestment at an unrealistically high rate.