XNPV function
Returns the net present value for a schedule of cash flows that is not necessarily periodic. To calculate the net present value for a series of cash flows that is periodic, use the NPV function.
Syntax
XNPV(rate,values,dates)
Rate is the discount rate to apply to the cash flows.
Values is a series of cash flows that corresponds to a schedule of payments in dates. The first payment is optional and corresponds to a cost or payment that occurs at the beginning of the investment. If the first value is a cost or payment, it must be a negative value. All succeeding payments are discounted based on a 365day year. The series of values must contain at least one positive value and one negative value.
Dates is a schedule of payment dates that corresponds to the cash flow payments. The first payment date indicates the beginning of the schedule of payments. All other dates must be later than this date, but they may occur in any order.
Remarks

Microsoft Office Excel stores dates as sequential serial numbers so they can be used in calculations. By default, January 1, 1900 is serial number 1, and January 1, 2008 is serial number 39448 because it is 39,448 days after January 1, 1900. Microsoft Excel for the Macintosh uses a different date system as its default.

Numbers in dates are truncated to integers.

If any argument is nonnumeric, XNPV returns the #VALUE! error value.

If any number in dates is not a valid date, XNPV returns the #VALUE! error value.

If any number in dates precedes the starting date, XNPV returns the #NUM! error value.

If values and dates contain a different number of values, XNPV returns the #NUM! error value.

XNPV is calculated as follows:
where:
di = the ith, or last, payment date.
d1 = the 0th payment date.
Pi = the ith, or last, payment.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example

Create a blank workbook or worksheet.

Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

In the worksheet, select cell A1, and press CTRL+V.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

