Simple ROI and internal rate of return (IRR) answer related but fundamentally different questions. Simple ROI calculates a percentage return without regard to timing. IRR calculates the exact discount rate at which the net present value of a series of cash flows equals zero — a measure that fully accounts for when each dollar is received and when each cost is incurred.
Informational calculation reference only.
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Why this metric dictates profitability
Two projects with identical simple ROI figures can have dramatically different IRRs when their cash flows differ in timing. A project that returns most of its cash in year 1 has a higher IRR than one that delivers the same total cash in year 5, because early cash flows can be reinvested sooner. Using simple ROI to choose between projects with different timing profiles systematically misprices the value of time.
Equation and data inputs
Simple ROI:
\text{ROI} = \frac{\text{Total Cash Received} - \text{Initial Investment}}{\text{Initial Investment}}
Net Present Value (NPV) at discount rate $k$:
\text{NPV} = \sum_{t=0}^{n} \frac{CF_t}{(1+k)^t}
Internal Rate of Return (IRR) — the value of $r$ that makes NPV = 0:
0 = \sum_{t=0}^{n} \frac{CF_t}{(1+r)^t}
IRR has no closed-form solution for $n > 2$ and is solved numerically through iterative approximation.
Benchmark ranges
Two projects each require a $100,000 investment and return $150,000 in total cash flows:
| Metric | Project A (front-loaded) | Project B (back-loaded) |
|---|---|---|
| Year 0 | −$100,000 | −$100,000 |
| Year 1 | $80,000 | $10,000 |
| Year 2 | $40,000 | $20,000 |
| Year 3 | $30,000 | $120,000 |
| Simple ROI | 50% | 50% |
| IRR | 36.3% | 14.0% |
| NPV at 10% | $30,540 | $11,420 |
Common variable mistakes
Using simple ROI for capital budgeting decisions across different timelines. When projects have different durations or timing profiles, simple ROI does not produce an accurate ranking. IRR or NPV should be used instead.
Interpreting IRR as a standalone return metric without a hurdle rate. IRR is only meaningful relative to the cost of capital or required rate of return. A project with a 15% IRR is attractive if capital costs 8% and unattractive if capital costs 18%.
Relying on IRR when cash flows change sign multiple times. When a project has periods of negative cash flow followed by positive, then negative again (common in real estate with capital expenditure cycles), multiple IRR solutions exist. Modified IRR (MIRR) resolves this by assuming reinvestment at a specified rate.
Use the ROI calculator to model both simple and multi-period return calculations for investment comparison.
Disclaimer: While we strive for absolute mathematical precision, actual real-world financial outcomes may vary based on institutional fees, localized tax brackets, changes in federal legislation, or fluctuating market indexes.