Formula Excel IRR

What this does

NPV discounts future cash flows back to today at a chosen rate and nets them against the upfront investment; a positive NPV means the project beats that rate. IRR is the discount rate at which NPV is exactly zero. The classic trap is that Excel's NPV assumes every value in its range sits one period in the future — so the year-0 investment must be added outside the function, while IRR wants the full series including year 0. The same idea underpins a lot of everyday Excel work, so the few minutes spent getting it right here pay back across every sheet you build afterwards. Treat it as a pattern, not a one-off, and it stops being something you look up and starts being something you reach for. For “formula excel irr”, the reliable version is a short checking loop, not just the first command that appears to work. Run it on a deliberately small range first, watch how the affected formula change, and only then apply the same setup to the full sheet. When a formula is involved, keep the inputs labelled beside it, reference cells instead of typing values, and apply number formatting only after the result checks out. That is what makes a calculation you can defend to a CFO or an auditor useful in real work: repeatable, auditable, and not dependent on memory or luck.

A worked example

B1 holds -10000 (investment today), B2:B4 hold 3000, 4200, 6800. =NPV(10%,B2:B4)+B1 returns €1,307.29 — the project creates value at a 10% hurdle rate. =IRR(B1:B4) returns 16.36%, the rate at which the same series breaks even. NPV and IRR are the standard go/no-go arithmetic for investments, equipment purchases, and projects — and the off-by-one-period NPV trap is probably the most common spreadsheet finance error. A practical tip before you scale it up: build it once on a small block of test data, confirm the number against the tool on this page, and only then point it at your real sheet. That one habit catches almost every mistake while it is still cheap to fix, long before a wrong figure reaches a report or a colleague.

In Google Sheets

If you are in Google Sheets rather than Excel, the good news is that the formula shown here is identical and the workflow barely changes — menus sit across the top instead of in a ribbon, and a few function names differ slightly, but anything you build here moves across with little or no rework. Nothing on this page is behind a login: the tool runs entirely in your browser, the formula is shown in full with one-click copy, and the steps work the same on Windows and Mac. That is the whole promise here — the exact answer, a way to prove it on your own numbers, and just enough context to make it stick. The short version of “formula excel irr”: the answer is at the top of this page, the tool proves it on your own numbers, and the sections above explain why it holds so the next variation does not stump you. Excel rewards people who reference cells instead of typing values and who keep inputs separate from formulas, because that is what makes a result you can audit months later. Build it once, deliberately, with the live tool as a check, and you convert a one-off lookup into a reusable skill — which is the whole point of learning the why and not just the what.

Common mistakes

• Including the year-0 investment inside the NPV range, which discounts it one year too many.
• Feeding IRR a series with no sign change — it needs at least one negative and one positive flow.
• Comparing projects of different lengths by IRR alone; NPV at a common rate is the safer ranking.
• Using annual NPV/IRR on monthly flows — switch the rate to a monthly rate or use XNPV/XIRR with real dates.

Frequently asked questions