About this tool
IRR / NPV / XIRR Calculator is a free, in-browser tool that computes the internal rate of return and net present value of a cash-flow series you type in — one flow per line, negatives for money out and positives for money in. Switch to dated mode and each line takes a YYYY-MM-DD date so irregular timing is handled exactly like a spreadsheet XIRR.
The IRR is the rate r that makes Σ CF_k/(1+r)^(t_k) equal zero; the tool finds it by scanning for a sign change and then bisecting with a capped iteration count, so it never spins or returns infinity. In dated mode t_k is the actual day count from the first flow divided by 365, which makes the result an annualized rate. NPV is evaluated separately at whatever discount rate you enter.
It is the standard way to measure the true return of a mutual-fund SIP, a rental property, or any project with uneven deposits and withdrawals. Everything runs locally in your browser — your cash flows are never uploaded.