NPV and IRR calculator
Enter a project's cash flows, the first being today's, and a discount rate. It gives the net present value, the internal rate of return, and whether to accept the project.
How it works
NPV = Σ CFt ÷ (1 + r)t, t = 0, 1, …, N
The IRR is the rate that makes the NPV zero. A project is worth doing when its NPV is above zero, which for conventional cash flows (one outflow, then inflows) is the same as its IRR being above the required return.
A worked example
A project costs 1,000 today and returns 300, 420 and 680 over the next three years. At a 10% discount rate the NPV is 130.73, so it adds value. The IRR is 16.34%: the rate at which the NPV falls to zero. Because the IRR is above 10%, the two rules agree.
Common mistakes on the exam
- The first cash flow is at time 0 and is not discounted; discounting it is the most common slip.
- When flows change sign more than once there can be several IRRs, or none. NPV is always well defined, which is why it is the preferred rule.
- IRR and NPV can rank mutually exclusive projects differently, because IRR ignores scale and assumes reinvestment at the IRR. Choose by NPV.
Where this is taught
- Work out net present value and the internal rate of return
- Differentiate the internal rate of return and time-weighted return when applied to alternatives
- Work out a project's internal rate of return and net present value, and explain each
Read the guide
Practise what you read
Questions people ask
What does a positive NPV mean?
The present value of the inflows exceeds the cost at your required return, so the project adds that much value. A negative NPV destroys value at that required return.
Why can there be more than one IRR?
The IRR is a root of a polynomial in (1 + r). Every time the cash flows change sign there can be another root, so a project with an outflow, then inflows, then a closing outflow can have two.
Should I use NPV or IRR?
NPV, whenever they could disagree. NPV measures the value created in currency; IRR is a rate, which says nothing about scale and can mislead on mutually exclusive projects.
Practise this until the arithmetic is automatic: questions on every topic, with the reason each wrong option is wrong.
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