NPV and IRR calculator
Type a row of cash flows and appraise the project: NPV at your required rate, the internal rate of return where the NPV curve crosses zero, and how long the discounted cash takes to pay the outlay back.
NPV against the discount rate
The IRR is where the curve crosses zero: the rate at which the project breaks even in present-value terms. Accept when the NPV at your required rate is positive.
NPV or IRR?
NPV answers "is this worth doing at my cost of capital"; IRR answers "how hard does the project work per pound in". They usually agree on accept/reject, but NPV is the safer judge when comparing projects of different sizes, and the IRR can fail to exist or fail to be unique when the cash flows change sign more than once — try a row like -100, 250, -155 and watch the curve cross zero twice.
Make it stick. Studying CM1 or CB1? Project appraisal is core syllabus. The notation cheat sheet covers the symbols. Memori is a flashcard app built by actuarial students — join the beta.
For education only, not financial advice.