NPV (net present value) and IRR (internal rate of return) test whether an investment is worth it, by valuing future cash flows in today’s money. Enter what money goes out and comes in, and when. See whether it beats your required return (NPV), and the single annualized return it actually produced (IRR) - the general-purpose version for any multi-year cash flow. For a property investment with a mortgage, rent, and running costs, the real estate IRR calculator builds all of that in.
NPV asks: "discounted back to today at my required return, is this deal worth more or less than what I'm putting in?" A positive NPV means the deal beats your discount rate; negative means it doesn't, even if the raw total of future cash looks impressive. IRR asks a related but different question: "what rate would make this deal exactly break even against itself?" It's the single annualized return baked into the actual cash flows - down payment now, income over the years, proceeds at the end - not an average, and not something you can look up, only solve for.
NPV has a straightforward formula: sum each cash flow divided by (1+rate)year. IRR is the rate that makes that sum exactly zero - but with more than two cash flows, there's no algebraic way to isolate it. This tool solves it the way Excel does internally: Newton-Raphson iteration, refining a guess using the slope of the NPV curve until it converges on the rate where NPV crosses zero, with a bisection fallback for cash-flow patterns where that doesn't converge cleanly.
Put $100,000 in (year 0, entered as negative - it's money going out). Get back $22,000 a year for four years, then $42,000 in year 5 - a bigger final year, whether that's a lump sum, an exit, or just a bigger year. Discounted at 8%, that comes to an NPV of about $1,451 - small and positive, so it clears an 8% hurdle, but not by much. Solved the other way, the IRR is about 8.50% - the single annualized return those exact cash flows produced. Compare that against what else the money could have earned to see whether the deal was actually worth doing, not just profitable in absolute dollars. For a property investment specifically - purchase price, a mortgage eating into rental income, and sale proceeds at the end - the real estate IRR calculator builds all of that in, including the levered, equity-level return most property investors actually care about.
This is the same present-value principle explained on the retirement calculator - just applied to cash flows that move in both directions over time instead of one lump sum. For growth expressed as a single annual rate instead of a cash-flow schedule - a salary, an investment, a business metric - see the CAGR calculator.
NPV is the value today of a series of future cash flows, discounted to account for the fact that money now is worth more than money later. A positive NPV means the investment is worth more than it costs.
NPV gives you a dollar figure at a discount rate you choose. IRR gives you the discount rate at which NPV would be zero - effectively the return the investment generates. NPV is the more reliable of the two when cash flows are irregular.
Your opportunity cost of capital - what the money could otherwise earn at similar risk, or your minimum acceptable return on this type of investment. There is no single correct number for every situation; a common starting benchmark is a diversified investment return (often 7-10%) or your actual cost of borrowing if the money is financed.
It means the investment, at the discount rate used, is expected to destroy value - the future cash flows are not worth enough today to justify what you would pay now. A negative NPV at your genuine opportunity cost of capital is a signal to look elsewhere, not necessarily that the numbers are wrong.
Yes, in unusual cases. If the cash flows change sign more than once - money out, then in, then out again - the equation can mathematically produce more than one valid IRR, or occasionally none. Most simple investments (money out once, then in) do not have this problem, but a project with a large cost partway through, like a mine needing rehabilitation, genuinely can.