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Free MIRR Calculator

Find the Modified Internal Rate of Return by discounting outflows at a finance rate and compounding inflows at a reinvestment rate.

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Ordinary IRR assumes every interim positive cash flow gets reinvested at the IRR itself — often unrealistic. MIRR fixes this by discounting negative cash flows back to today at a chosen finance rate, and compounding positive cash flows forward to the final period at a chosen reinvestment rate, then solving a single compound-growth equation between the two totals.

How it works

Enter each year's cash flow (negative for outflows, positive for inflows), a finance rate, and a reinvestment rate. Negative flows are discounted to year 0; positive flows are compounded to the final year; MIRR is the rate that grows the discounted outflow total into the compounded inflow total.

  1. Enter cash flow — Year 0.
  2. Enter cash flow — Year 1.
  3. Enter cash flow — Year 2.
  4. Enter cash flow — Year 3.
  5. Enter cash flow — Year 4 (optional).
  6. Enter cash flow — Year 5 (optional).
  7. Enter cash flow — Year 6 (optional).
  8. Enter finance rate (%).
  9. Enter reinvestment rate (%).
  10. Click Calculate to see your results.

Examples

A simple 4-year project

An initial $1,000 investment followed by inflows of $200, $300, $400, $500 (finance rate 10%, reinvestment rate 12%) gives a MIRR of about 12.56%.

Who should use it

  • Comparing capital projects with very different cash flow timing.
  • Capital budgeting decisions where reinvestment assumptions matter.

Industry applications

  • Corporate finance and capital budgeting
  • Investment analysis

Advantages

  • More realistic than plain IRR for projects with interim cash flows.
  • Always gives a single, unambiguous rate (unlike IRR, which can have multiple solutions for unconventional cash flow patterns).

Limitations

  • Requires choosing two rates instead of one, adding a layer of judgment.

Common mistakes to avoid

  • Using the same rate for both financing and reinvestment — the point of MIRR is that these can genuinely differ.

Best practices

  • Set the reinvestment rate to your actual expected return on interim cash (e.g. your cost of capital), not an optimistic guess.

Tips

  • Use the NPV Calculator alongside MIRR — a positive NPV and MIRR above your cost of capital should usually agree on whether to accept a project.

Frequently asked questions

IRR can give a misleadingly high number when it assumes interim cash flows are reinvested at that same high rate — MIRR uses a separate, more realistic reinvestment rate instead.
That's fine — every negative cash flow is discounted back to year 0 and summed before the final MIRR calculation.

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