MIRR Calculator

An expert tool to find the Modified Internal Rate of Return.

Calculation Breakdown per Period

Period	Cash Flow	PV Factor (Finance)	PV of Outflow	FV Factor (Reinvest)	FV of Inflow

What is a MIRR Calculator?

A MIRR calculator is a financial tool used to evaluate the attractiveness of an investment. MIRR stands for Modified Internal Rate of Return. Unlike the standard Internal Rate of Return (IRR), the MIRR provides a more realistic measure of profitability by making explicit assumptions about the rates at which cash flows are handled. Specifically, it assumes that positive cash flows are reinvested at a firm’s cost of capital (or another specified rate), and initial outlays are financed at the firm’s financing cost. This distinction solves major flaws in the IRR calculation, such as the potential for multiple rates of return and the unrealistic assumption that cash flows are reinvested at the IRR itself.

Financial analysts, corporate finance professionals, and savvy investors should use this tool when performing capital budgeting. It is superior for comparing mutually exclusive projects, especially those of different sizes or durations. A common misconception is that MIRR is just a minor tweak to IRR. In reality, it represents a fundamentally more sound approach to project evaluation by separating the financing and reinvestment decisions from the project’s intrinsic returns.

MIRR Formula and Mathematical Explanation

The formula for the Modified Internal Rate of Return (MIRR) is designed to find a single rate of return that equates the present value of a project’s costs with the future value of its returns. The calculation is a multi-step process.

The core formula is:

MIRR = [ (FV_{Positive Cash Flows} / PV_{Negative Cash Flows})^(1/n) ] – 1

Here’s a step-by-step breakdown:

1. Calculate the Present Value (PV) of all negative cash flows (outflows). This includes the initial investment at period 0 and any subsequent negative cash flows. Each negative cash flow is discounted back to period 0 using the Finance Rate.
2. Calculate the Future Value (FV) of all positive cash flows (inflows). Each positive cash flow is compounded forward to the end of the project’s life (period n) using the Reinvestment Rate.
3. Solve for MIRR. With the PV of costs and FV of returns, the formula finds the single discount rate (the MIRR) that makes the two equivalent over the project’s life.

Variables in the MIRR Calculation

Variable	Meaning	Unit	Typical Range
PVNegative Cash Flows	The sum of all investment costs discounted to today’s value.	Currency ($)	Positive Value
FVPositive Cash Flows	The sum of all positive cash flows compounded to the end of the project.	Currency ($)	Positive Value
n	The total number of periods (usually years).	Integer	1 – 50+
Finance Rate	The cost of capital used to finance the project’s outlays.	Percentage (%)	2% – 15%
Reinvestment Rate	The rate at which positive cash flows are assumed to be reinvested.	Percentage (%)	2% – 20%

Practical Examples of Using a MIRR Calculator

Understanding how to use a MIRR calculator is best illustrated with real-world examples. These scenarios showcase how the calculator helps in making sound financial decisions.

Example 1: Evaluating a New Manufacturing Plant

A company is considering a project to build a new plant. The numbers are as follows:

• Initial Investment: $2,000,000
• Cash Flows (Years 1-5): $400,000, $500,000, $600,000, $700,000, $800,000
• Finance Rate (Cost of Debt): 6%
• Reinvestment Rate (WACC): 10%

Using our MIRR calculator, we find the PV of outflows is the initial $2,000,000. The FV of inflows at the 10% reinvestment rate is calculated to be $3,488,440. The MIRR is approximately 11.78%. Since this is significantly higher than both the finance rate and the reinvestment rate, the project is financially attractive.

Example 2: Comparing Two Mutually Exclusive Tech Projects

A tech firm has to choose between two projects, A and B.

• Project A: Initial Investment: $500,000; CFs: $150k, $200k, $250k, $300k.
• Project B: Initial Investment: $800,000; CFs: $250k, $300k, $350k, $400k.
• Finance Rate: 7%
• Reinvestment Rate: 12%

The MIRR calculator shows Project A has a MIRR of 20.5%, while Project B has a MIRR of 17.9%. Even though Project B is larger, Project A offers a higher quality return relative to its investment size. The MIRR provides a clear basis for comparison, suggesting Project A is the better choice for capital allocation efficiency. This is a key part of Project Profitability Analysis.

How to Use This MIRR Calculator

Our how to calculate mirr using financial calculator tool is designed for ease of use and accuracy. Follow these steps to get your result:

1. Enter the Initial Investment: Input the total upfront cost of the project as a positive number.
2. Provide the Cash Flows: In the text area, list the cash flows for each period (e.g., year) separated by commas. Use negative numbers for any additional costs (outflows) and positive numbers for returns (inflows).
3. Set the Finance Rate: Enter the interest rate the company pays on the capital used for the investment. This is often the firm’s cost of debt.
4. Set the Reinvestment Rate: Enter the rate at which you assume the positive cash flows can be reinvested. This is typically the company’s Weighted Average Cost of Capital (WACC) or another opportunity cost. For more details, see our guide on the Reinvestment Rate Assumption.

The calculator instantly updates the MIRR, intermediate values, table, and chart. The primary result is highlighted for clarity. Use the “Copy Results” button to save your analysis. A high MIRR relative to your cost of capital indicates a potentially strong investment.

Key Factors That Affect MIRR Results

The result from a MIRR calculator is sensitive to several key inputs. Understanding these factors is crucial for accurate financial modeling.

• Finance Rate: A higher finance rate increases the present value of any negative cash flows after period zero, which in turn lowers the MIRR. It reflects the cost of borrowing and directly impacts the perceived cost of the project.
• Reinvestment Rate: This is one of the most significant factors. A higher reinvestment rate inflates the future value of positive cash flows, leading to a higher MIRR. This rate should realistically reflect the company’s investment opportunities.
• Timing of Cash Flows: Cash flows received earlier have a greater impact on the MIRR because they have more time to be reinvested and compounded. Projects with strong early returns will generally show a better MIRR.
• Size and Frequency of Negative Cash Flows: Projects with ongoing capital injections (negative cash flows) will have a higher PV of outflows, which reduces the MIRR. The timing and magnitude of these costs are critical.
• Project Duration (n): A longer project life provides more periods for reinvestment returns to compound, but it also means the final MIRR is an annualized rate over a longer term, which can sometimes dilute very high returns from short-term projects.
• Initial Investment Amount: A larger initial investment relative to the subsequent positive cash flows will naturally lead to a lower MIRR. The efficiency of capital deployment is a core aspect of what MIRR measures.

Frequently Asked Questions (FAQ)

1. What is the main difference between IRR and MIRR?

The primary difference is the reinvestment rate assumption. IRR assumes cash flows are reinvested at the IRR itself, which can be unrealistically high. MIRR uses a more practical, user-defined reinvestment rate, such as the company’s cost of capital. This makes MIRR a more conservative and reliable metric.

2. Why does MIRR solve the multiple-IRR problem?

The multiple-IRR problem can occur with non-conventional cash flows (multiple changes in sign). Because MIRR aggregates all negative cash flows at time 0 and all positive cash flows at the terminal year, it creates a conventional cash flow pattern (one initial outflow, one terminal inflow), which mathematically guarantees only one unique solution.

3. What is a good MIRR?

A “good” MIRR is one that exceeds the project’s cost of capital (often the reinvestment rate used in the calculation). If the MIRR is higher than the rate of return you could get from an alternative investment of similar risk, the project is generally considered a good investment.

4. Can I use this MIRR calculator for any type of investment?

Yes, this MIRR calculator is versatile. It can be used for various capital budgeting decisions, such as real estate, equipment purchases, business acquisitions, or any project with an initial investment followed by a series of cash flows.

5. What should I use for the finance and reinvestment rates?

The Finance Rate should be your cost of borrowing for the project. The Reinvestment Rate is typically the Weighted Average Cost of Capital (WACC), as it represents the average return the company expects to make on its investments. Consult our WACC Calculator for help.

6. What if my project has negative cash flows in later years?

Our MIRR calculator handles this correctly. Any negative cash flow entered will be discounted back to the present value of outflows using the finance rate, ensuring an accurate calculation regardless of when the costs occur.

7. How does MIRR relate to Net Present Value (NPV)?

Both are sophisticated Capital Budgeting Techniques. If a project’s MIRR is greater than its cost of capital, its NPV will be positive. While MIRR gives a percentage return, NPV provides a dollar value of the project’s contribution to firm value. They generally lead to the same accept/reject decision for independent projects.

8. Is a higher MIRR always better when comparing projects?

Generally, yes. When comparing mutually exclusive projects, the one with the higher MIRR is often preferred as it indicates a more efficient use of capital. However, you should also consider project scale. A project with a slightly lower MIRR but a much larger positive NPV might create more absolute value for the company.