Returns the number of periods for an investment based on periodic, constant payments and a constant interest rate.
 | Rate | is the interest rate per period. |
| Pmt | is the payment made each period; it cannot change over the life of the annuity. Typically, pmt contains principal and interest but no other fees or taxes. |
| Pv | is the present value, or the lump-sum amount that a series of future payments is worth right now. |
 | Fv | is the future value, or a cash balance you want to attain after the last payment is made. If fv is omitted, it is assumed to be 0 (the future value of a loan, for example, is 0). |
| Type | is the number 0 or 1 and indicates when payments are due. If type is omitted, it is assumed to be 0. |
