Formula for Internal Rate of Return in Excel

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. The difference between a quick fix and a sheet you can trust is the extra minute you spend validating “formula for internal rate of return in excel”. Start on a copy or a tiny sample, keep the affected formula visible, and compare the result with the outcome you expected before you touch the real workbook. 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. The point is a calculation you can defend to a CFO or an auditor, but the practical win is that someone else can open the file and understand what happened without asking you.

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. Check the referenced cells, argument order and result type in your workbook. Start with the worked example before changing an input, then compare the changed result with the calculation you expected. An error value or a result of a different type is a reason to inspect the inputs and arguments.

In Google Sheets

Google Sheets support for this task has not been verified. Check the function, arguments and workflow in the target product before transferring the example. Matching formula notation does not establish identical behaviour. The aim was to get you unstuck fast and leave you a little more capable than a copy-paste would. The answer is at the top and the detail above shows why it holds — so the next time a colleague asks, you can answer without reaching for search. For “formula for internal rate of return in excel”, keep the input cells and the result visible while you check the formula in Excel. Follow the worked example and change one input at a time. The steps explain the workbook calculation; this page does not run a live calculator for that task.

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