Financial.NPer Method (Double, Double, Double, Double, DueDate)
Note 

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Returns a Double specifying the number of periods for an annuity based on periodic fixed payments and a fixed interest rate.
Assembly: Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)
public static double NPer( double Rate, double Pmt, double PV, double FV = 0, DueDate Due = DueDate.EndOfPeriod )
Parameters
 Rate

Type:
System.Double
Required. Double specifying interest rate per period. For example, if you get a car loan at an annual percentage rate (APR) of 10 percent and make monthly payments, the rate per period is 0.1/12, or 0.0083.
 Pmt

Type:
System.Double
Required. Double specifying payment to be made each period. Payments usually contain principal and interest that does not change over the life of the annuity.
 PV

Type:
System.Double
Required. Double specifying present value, or value today, of a series of future payments or receipts. For example, when you borrow money to buy a car, the loan amount is the present value to the lender of the monthly car payments you will make.
 FV

Type:
System.Double
Optional. Double specifying future value or cash balance you want after you have made the final payment. For example, the future value of a loan is $0 because that is its value after the final payment. However, if you want to save $50,000 over 18 years for your child's education, then $50,000 is the future value. If omitted, 0 is assumed.
 Due

Type:
Microsoft.VisualBasic.DueDate
Optional. Object of type DueDate that specifies when payments are due. This argument must be either DueDate.EndOfPeriod if payments are due at the end of the payment period, or DueDate.BegOfPeriod if payments are due at the beginning of the period. If omitted, DueDate.EndOfPeriod is assumed.
Return Value
Type: System.DoubleReturns a Double specifying the number of periods for an annuity based on periodic fixed payments and a fixed interest rate.
Exception  Condition 

ArgumentException  Rate <= 1. 
ArgumentException  Rate = 0 and Pmt = 0 
An annuity is a series of fixed cash payments made over a period of time. An annuity can be a loan (such as a home mortgage) or an investment (such as a monthly savings plan).
For all arguments, cash paid out (such as deposits to savings) is represented by negative numbers; cash received (such as dividend checks) is represented by positive numbers.
This example uses the NPer function to return the number of periods during which payments must be made to pay off a loan whose value is contained in PVal. Also provided are the interest percentage rate per period (APR / 12), the payment (Payment), the future value of the loan (FVal), and a number that indicates whether the payment is due at the beginning or end of the payment period (PayType).
Sub TestNPer() Dim TotPmts As Double Dim PVal, APR, Payment As Double Dim PayType As DueDate Dim Response As MsgBoxResult ' Usually 0 for a loan. Dim Fval As Double = 0 PVal = CDbl(InputBox("How much do you want to borrow?")) APR = CDbl(InputBox("What is the annual percentage rate of your loan?")) ' Usually 0 for a loan. If APR > 1 Then APR = APR / 100 Payment = CDbl(InputBox("How much do you want to pay each month?")) Response = MsgBox("Do you make payments at the end of month?", MsgBoxStyle.YesNo) If Response = MsgBoxResult.No Then PayType = DueDate.BegOfPeriod Else PayType = DueDate.EndOfPeriod End If TotPmts = NPer(APR / 12, Payment, PVal, FVal, PayType) If Int(TotPmts) <> TotPmts Then TotPmts = Int(TotPmts) + 1 MsgBox("It will take you " & TotPmts & " months to pay off your loan.") End Sub
Available since 1.1