Calculates the number of payment periods for an investment based on constant-amount periodic payments and a constant interest rate.

**Sample Usage**

NPER(3,550,4000)

NPER(C2,C3,C4,C5)

**Syntax**

NPER(rate, payment_amount, present_value, [future_value], [type])

- rate - The rate of interest.

- payment_amount - The amount of each payment made.
- present_value - The present value of the investment.
- future_value - [OPTIONAL] The future value remaining after the final payment has been made.
- type - [OPTIONAL] The due date type for the payment – at the beginning (0) or end of each period (1).

**Examples**

NPER(3,550,4000) returns -2.25, the number of payment periods for the investment.

NPER(C2,C3,C4,C5) returns the periods for the investment with the given terms.

**Notes**

- Ensure that consistent units are used for rate and payment_amount.