IRR is the discount rate at which an investment’s net present value equals exactly zero — effectively, the rate of return the cash flows actually earn.
How it works
For most real cash flow patterns, there’s no algebraic way to isolate the rate directly — this calculator numerically searches (by bisection) for the rate where NPV crosses zero, the same method every real-world IRR tool, spreadsheet functions included, actually uses.
The complementary question to NPV
NPV asks “how much value does this create at a discount rate I specify?” IRR asks “what discount rate would make this investment exactly break even?” — a rate you can compare directly against other opportunities, without picking a discount rate first. An IRR above your actual cost of capital is the same signal as a positive NPV at that same rate; the two methods agree by construction.
How to use this calculator
- Enter the upfront investment.
- List each year’s expected cash flow.
- Read the resulting rate of return.
Frequently asked questions
Why can’t IRR be solved with a direct formula?
Because it requires finding the root of a polynomial whose degree depends on how many cash flow periods there are — for more than a couple of periods, there’s no general algebraic solution, only a numerical search.
Can an investment have more than one IRR, or none?
Yes, for cash flows that change sign more than once (an outflow, then inflows, then another outflow, for instance) — a real limitation of the concept itself, not a shortcoming specific to this calculator. This calculator handles the ordinary pattern (one upfront outflow, then inflows) and declines outside that.
What’s a “good” IRR?
There’s no universal answer — compare it against your actual alternative: what else you could realistically earn on the money at a similar risk level.
Why does adding more years of positive cash flow not always raise the IRR by much?
Because later cash flows are discounted more heavily in the search — a few more years of the identical cash flow contributes proportionally less to the rate than the earlier, less-discounted years already did.
How is this related to the NPV calculator?
Same underlying cash flow math — IRR finds the rate where that calculator’s NPV output would read exactly zero, rather than computing NPV at a rate you specify.
