How this calculator works
Internal rate of return answers the question a required-return discount rate cannot: instead of telling you the dollar value of a project at a rate you choose, IRR solves for the exact rate at which the project neither adds nor destroys value — the rate at which net present value (NPV) is zero.
There is no algebraic formula that isolates the rate for most cash-flow patterns, so this calculator finds it numerically. It scans a wide range of possible rates, from -99% up to 1,000%, for the point where NPV crosses from positive to negative (or vice versa), then narrows in on that point by repeated bisection until NPV is effectively zero.
The formula
IRR is the rate r that solves: 0 = −Initial investment + Σ [CFₜ ÷ (1 + r)ᵗ] for t = 1 to nThis equation generally cannot be solved algebraically for more than two cash flows, so IRR is found by searching for the rate numerically rather than computing it directly.
Worked example: $10,000 investment over 4 years
- Cash flows of $3,000, $4,000, $5,000 and $2,000 arrive at the end of years 1 through 4.
- At a 10% discount rate, NPV is positive (about +$1,155.66), which means the true break-even rate must be higher than 10%.
- Searching upward, NPV crosses zero at approximately 15.32%.
- Checking the answer: discounting all four cash flows at 15.32% and subtracting the $10,000 investment gives an NPV of essentially $0, confirming 15.32% is the IRR.
Frequently asked questions
How is IRR different from NPV?
NPV gives a dollar amount at a discount rate you supply. IRR instead solves for the discount rate that makes NPV exactly zero, producing a percentage you can compare directly against your required rate of return or cost of capital.
What does it mean if this calculator can't find an IRR?
It means no discount rate between -99% and 1,000% makes NPV cross zero for the cash flows entered — typically because every cash flow is zero or negative, so the investment never recovers any value at any rate in that range.
Can a set of cash flows have more than one IRR?
Yes, if the cash flows change sign more than once (for example, a large cost partway through a project), NPV can cross zero at more than one rate. This calculator reports the first sign change it finds scanning from -99% upward, which may not be the only one.
Is a higher IRR always better?
A higher IRR generally means a more attractive rate of return, but IRR does not account for the size of the investment or the actual dollar value created, which is what NPV measures. A very high IRR on a tiny investment can create less value than a modest IRR on a large one.
What IRR counts as a good result?
It depends entirely on your required rate of return or cost of capital. An IRR above that required rate suggests the investment is expected to add value; below it suggests the opposite. There is no universal good IRR that applies to every situation.