Skip to main content
Financial Planning

Internal Rate of Return (IRR) Calculator

Find the internal rate of return (IRR) of a cash-flow series, plus the modified IRR (MIRR) using your finance and reinvestment rates.

Your inputs

Results

IRR per period

15.3221%

MIRR per period
12.1944%
Undiscounted net cash flow
4,000

✓Exact calculation — rounded only for display

Inputs are never added to links for financial, salary or health calculators.

What this calculator does

IRR is the discount rate at which a project’s NPV equals zero — its break-even rate of return. MIRR fixes IRR’s unrealistic reinvestment assumption and always has a single answer.

Formula and method

IRR: solve Σ CFₜ ÷ (1 + IRR)^t = 0 (numerically). MIRR = (FV of positive flows at reinvestment rate ÷ PV of negative flows at finance rate)^(1/n) − 1

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Cash flows from period 0 (investment as negative): -10000, 3000, 4000, 5000, 2000
  • Finance rate (for MIRR): 8 %
  • Reinvestment rate (for MIRR): 8 %

Results

  • IRR per period: 15.3221%
  • MIRR per period: 12.1944%
  • Undiscounted net cash flow: 4,000

How to read the results

Accept projects whose IRR exceeds your required return. When cash flows change sign more than once, several IRRs may exist — rely on NPV or MIRR.

Assumptions and limitations

  • The solver searches between −99 % and 1000 % and reports the root closest to 0 %.

Financial results are estimates based on the inputs and assumptions shown. They are not financial advice; confirm figures with your lender, provider or a qualified adviser before making decisions.

Questions

Why can IRR be misleading?

It assumes interim cash flows are reinvested at the IRR itself, which may be unrealistic for high IRRs, and it can rank projects of different sizes incorrectly.

Methodology and verification

Result type
Exact mathematical calculation (rounded only for display)
Formula version
1.0
Automated verification
3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

Privacy

Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Because this calculator can involve personal financial or health details, your inputs are never added to share links or saved to history. Privacy policy