Installment Loan Calculation and File Application
This application calculates any one of the four monthly installment loan factors given the other three and provides the option to save the named loan for subsequent retrieval and editing. To use: fill in any three of the four text boxes, touch “Calculate” and the blank factor will be calculated. To clear a factor touch the circled x on the right side of the applicable text box. To save the loan data fill in the “Loan Name” field, touch “Save” and the name will appear in the picker located in the lower part of the screen. To retrieve a loan slide the picker until the desired loan name appears in the center position.
The four factors of a monthly installment loan such as a car loan or home mortgage are: 1. LoanAmt — Original loan amount,
2. IntRate — Annual interest rate being charged by the lender,
3. NuMos — Number of months required to pay off the loan,
4. MoPmt — Amount of monthly payment.
Calculation Logic:
MoPmt = LoanAmt * IntRate / (1 - (1 + IntRate) ^ -NuMos)
IntRate uses above formula to iterate IntRate from 0.0 by 0.001% until MoPmt is equal or greater than the given amount.
NuMos = Log(MoPmt / (MoPmt - LoanAmt * IntRate)) / Log(1 + IntRate)
LoanAmt = MoPmt * (1 - (1 + IntRate) ^ NuMos) / IntRate
This application rounds the results: MoPmt to nearest penny, IntRate to three decimal places, NuMos to two decimal places and LoanAmt to nearest dollar.