XIRR

XIRR = IRR for series: Computes the internal rate of return (IRR) for a non-periodic cash flow, i.e., where each payment made or received occurs on an arbitrary date, rather than at periodic intervals.
Computes the Internal Rate of Return (IRR) for a series of equally spaced cash flows («values») along the index «I». The internal rate of return is a widely used criteria for comparing alternative capital investment opportunities. Intuitively, it is the effective compounded rate of return (per time step) on invested capital that is implied by the investment's future cash flows.

IRR is an indicator of the efficiency or quality of an investment, but gives no information about the magnitude of the return. An investment with an IRR exceeding an organization's cost of capital adds value to the organization.

The IRR is formally defined as the discount rate at which the Net Present Value of the cash flows is equal to zero. For many "normal" capital investments, a large up-front outlay is followed by a stream of revenue into the future eventually totalling an amount greater than the initial investment. For these cash flows, as discount rate increases, NPV decreases, eventually passing from positive to negative NPV. The discount rate where NPV passes through zero, the IRR, is the discount rate at which the project's value of future earnings is break-even with the initial investment cost.

Internal rate of return (IRR) is a method of calculating an investment’s rate of return. The term internal refers to the fact that the calculation excludes external factors, such as the risk-free rate, inflation, the cost of capital, or financial risk.

The method may be applied either ex-post or ex-ante. Applied ex-ante, the IRR is an estimate of a future annual rate of return. Applied ex-post, it measures the actual achieved investment return of a historical investment.

It is also called the discounted cash flow rate of return (DCFROR).