Periods()

Periods()

Number of Periods for a loan

Syntax

`      Periods( nLoan, nPayment, nInterest ) --> nPeriods`

Arguments

<nLoan> amount of money you get from the bank <nPayment> amount of money you pay back per period <nInterest> rate of interest per period, 1 == 100%

Returns

<nPeriods> number of Periods you need to pay the loan back

Description

Periods() calculates the number of Periods one needs to pay back a loan of <nLoan> with periodical payments of <nPayment> and for a rate of interest <nInterest> per period.

debt in period 0 = <nLoan>
debt in period 1 = ((debt in period 0)-<nPayment>)*(1+<nInterest>/100)
debt in period 2 = ((debt in period 1)-<nPayment>)*(1+<nInterest>/100) etc…
debt in period <nPeriod> = ((debt in period <nPeriod>-1)-<nPayment>)*(1+<nInterest>/100)

-> has to be 0, so

<nPeriods> = -log(1-<nLoan>*(<nInterest>/100)/<nPayment>)/log(1+<nInterest>/100))

Note, however that in the case of nPayment <= <nLoan>*(<nInterest>/100), one would need infinite time to pay the loan back. The functions does then return -1.

Examples

```      // You get a loan of 5172.56 at a interest rate of 0.5% per
// month (6% per year).
// You can afford to pay 100 back every month, so you need

? Periods( 5172.56, 100, 0.005 ) // --> 60.0

// months to cancel the loan.```

Tests

```      Periods( 5172.56, 100, 0.005 ) == 60.0
Periods( 5172.56, 100, 0.0 ) == 51.7256```

Compliance

Periods() is compatible with CT3’s Periods().

Platforms

All

Files

Source is finan.c, library is libct.

Seealso

PV(), FV(), PAYMENT(), RATE()