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**PERS**(//presentvalue,rate,payment,futurevalue//)

| **PERS** | Computes the number of periods required to reach a targeted future value. |
| //presentvalue// | A numeric constant or variable containing the present value of the investment. |
| //rate// | A numeric constant or variable containing the //periodic //rate of return. |
| //payment// | A numeric constant or variable containing the periodic payment. |
| //futurevalue// | A numeric constant or variable containing the amount of the desired or targeted future value of the investment. |

**PERS **determines the number of periods required to reach a desired amount (//futurevalue//) based upon a starting amount (//presentvalue//), a periodic interest rate (//rate//), and a payment amount (//payment//). If payments occur at the beginning of each period, use the PREPERS function, which takes into account the added interest earned on each period's payment.

Periodic rate may be calculated as follows:

PeriodicRate = AnnualInterestRate / (PeriodsPerYear * 100)

{{c6h0012.jpg|C6H0012.jpg}}

If the present value is less than the future value (annuities), payments are positive, and conversely, if the present value is greater than the future value (loans), payments are negative.

**Return Data Type:**     DECIMAL

**Internal Formulas:**

{{pers.jpg|PERS.jpg}}

The PERS function performs binary search iterations to home in on the periods value. If more than 50 such iterations are required, a value of zero is returned.

**Example:**

**  PeriodicRate = AnnualRate / (PeriodsPerYear * 100)**

**  IF TimeOfPayment = 'Beginning of Periods'**

**   TotalPeriods = PREPERS(PresentValue,PeriodicRate,Payment,FutureValue)**

**  ELSE**

**   TotalPeriods = PERS(PresentValue,PeriodicRate,Payment,FutureValue)**

**  END**