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IRR Explained: How to Calculate the True Return on Your Investment

September 26, 2026

What Is IRR?

The Internal Rate of Return (IRR) is the discount rate that makes the Net Present Value (NPV) of all cash flows from an investment equal to zero. In simpler terms, it's the annualized rate of return that an investment is expected to generate.

Unlike simple ROI, IRR accounts for the timing of cash flows — making it a more accurate measure of investment performance.

Why IRR Matters

Time Value of Money

IRR recognizes that receiving R100,000 in Year 1 is more valuable than receiving R100,000 in Year 5. This is crucial for comparing investments with different cash flow patterns.

Universal Comparison

IRR gives you a single percentage that you can compare across different types of investments — property, stocks, business ventures, or bonds.

Decision Rule

If IRR > your required rate of return (hurdle rate), the investment is worth pursuing. If IRR < hurdle rate, look elsewhere.

Real-World Example: Property Investment in Africa

You're considering buying a rental property in Nairobi for KES 5,000,000:

  • Year 1: KES 600,000 rental income
  • Year 2: KES 650,000
  • Year 3: KES 700,000
  • Year 4: KES 750,000
  • Year 5: KES 800,000 + KES 6,000,000 (sale)

The IRR of this investment would be approximately 18.5% — well above typical savings account rates of 5-7%.

IRR vs ROI vs NPV

| Metric | Considers Timing? | Single Number? | Best For |

|——–|——————-|—————-|———-|

| ROI | No | Yes | Quick comparisons |

| NPV | Yes | Yes (currency) | Absolute value added |

| IRR | Yes | Yes (%) | Comparing returns |

Limitations of IRR

  • Reinvestment assumption: IRR assumes cash flows can be reinvested at the same rate
  • Multiple IRRs: Non-conventional cash flows can produce multiple IRR values
  • Scale blind: A 50% IRR on R10,000 isn't as valuable as a 20% IRR on R1,000,000

FAQ

Q: What is a good IRR?

A: It depends on the investment type. Real estate: 8-12%. Private equity: 15-25%. Startups: 25%+. Always compare to your cost of capital.

Q: How is IRR calculated?

A: IRR is solved iteratively using the Newton-Raphson method. Our calculator handles this automatically.

Related Tools

This article is for general information only and is not financial, tax or legal advice. Rates, thresholds and regulations change — always confirm current figures with the relevant revenue authority or a qualified advisor before making a financial decision.