Thread: Monthly mortgage payment calculator

IM writing a monthly mortgage payment calculator I have the formula but dont know how to enter it:

the formula i have is

pmt = ((p-d)*r/12) / (1-(1+(r/12)^-m)

my code is:
import java.util.Scanner;

public class Project1 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);

System.out.println("Enter the price of the house: ");
double housePrice = input.nextDouble();
System.out.println("Enter the down payment: ");
double downPayment = input.nextDouble();
System.out.println("Enter the annual interest rate: ");
double annualInterestRate = input.nextDouble();
System.out.println("Enter the number of payments: ");
double numberofPayments = input.nextDouble();

double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+(annualInterestRate/12)^-numberofPayments))));







}
}
I dont know how to enter this formula maybe there is a simpler way?

--- Update ---

In which PMT is the monthly payment, P is the listed price of the house, D is the
down payment, r is the annual interest rate and m is the number of payments.

It's much easier to help you if we can easily read your code. Please surround your code with code tags:

[code]

//..... your code goes here

[/code]

Also, regarding your formula, have you had a chance to look at some of the methods available in the Math class? Some will come in handy for you such as Math.pow(....). Please have a look as you won't regret it!

 
 
 
import java.util.Scanner;
 
	public class Project1 {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
 
		System.out.println("Enter the price of the house: ");
		double housePrice = input.nextDouble();
		System.out.println("Enter the down payment: ");
		double downPayment = input.nextDouble();
		System.out.println("Enter the annual interest rate: ");
		double annualInterestRate = input.nextDouble();
		System.out.println("Enter the number of payments: ");
		double numberofPayments = input.nextDouble();
 
		double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+(annualInterestRate/12)^-numberofPayments))));
 
 
 
		System.out.println( (monthlyPayment+ " is the larger of the two numbers.");
 
 
 
	}	
	}

also Im somewhat aware of the math pow function but dont know how to fit it in this formula(not sure where it would go)

Originally Posted by iamgonge

also Im somewhat aware of the math pow function but dont know how to fit it in this formula(not sure where it would go)

Anywhere you see the little ^ in your math formula this can mean x to the power of y, while in Java it means something completely different (and not very useful for your purposes). I'd start there. Good luck!

ok tried it didnt work now what( I dont know how to write this code!!!!!!)
heres what i tried

double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+(annualInterestRate/12)math.pow-numberofPayments)))); <----dont know how to enter this last part its a negative exponent

--- Update ---

ok i think i got it does this look right?
double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+Math.pow(annualInterestRate/12, - numberofPayments)))));

The Math API will tell you how to use the method, but as in calling *any* method, you will need to use parentheses. You will need to separate your parameters by commas if you have multiple parameters.

As an aside: please do not multi-post the same question in the forum.

Originally Posted by iamgonge

ok i think i got it does this look right?
double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+Math.pow(annualInterestRate/12, - numberofPayments)))));

Test it out and see if the code works as expected.

so it doesnt seem to be computing correctly i keep getting negative number and they seem quite off, Is my formula wrtitten wrong?

--- Update ---

ok so this my program as of this moment, it runs but the math is wrong can someone please check my formula
[code]


import java.util.Scanner;

public class Project1 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);

System.out.println("Enter the price of the house: ");
double housePrice = input.nextDouble();
System.out.println("Enter the down payment: ");
double downPayment = input.nextDouble();
System.out.println("Enter the annual interest rate: ");
double annualInterestRate = input.nextDouble();
System.out.println("Enter the number of payments: ");
double numberofPayments = input.nextDouble();

double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+Math.pow(annualInterestRate/12, -numberofPayments)))));


System.out.println( "The price of the house is: " + housePrice);
System.out.println( "Your down payment is :" + downPayment);
System.out.println( "Your annual interest rate is :" + annualInterestRate);
System.out.println( "Your number of payments are :" + numberofPayments);
System.out.println( "Your monthly payment is :" + monthlyPayment);







}
}
/code

double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+Math.pow(annualInterestRate/12, -numberofPayments)))));

this is my formula and its not working please help?

ok changed it still doesnt work please check

 
 
import java.util.Scanner;
 
	public class Project1 {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
 
		System.out.println("Enter the price of the house: ");
		double housePrice = input.nextDouble();
		System.out.println("Enter the down payment: ");
		double downPayment = input.nextDouble();
		System.out.println("Enter the annual interest rate: ");
		double annualInterestRate = input.nextDouble();
		System.out.println("Enter the number of payments: ");
		double numberofPayments = input.nextDouble();
 
		double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+(Math.pow(annualInterestRate/12, -numberofPayments))))));
 
 
		System.out.println( "The price of the house is: " + housePrice);
		System.out.println( "Your down payment is :" + downPayment);
		System.out.println( "Your annual interest rate is :" + annualInterestRate);
		System.out.println( "Your number of payments are :" + numberofPayments);		
		System.out.println( "Your monthly payment is :" + monthlyPayment);
 
 
 
 
 
 
 
	}	
	}

Please edit your post above and fix your code tags. Your code is difficult to read. If it doesn't work, then please show what you've done to try to debug it (as per Norm's recommendations above), and the results of these efforts.

im not faqmiliar with this formula i dont know how to break it down in java code so i cant do what your saying are you saying assign this a variable (housePrice - downPayment) then assign this a variable (annualInterestRate/12)) and so on, ? I dont understand

ok this what i got i broke the formula into a top and a bottom
then printed out the results: heres the code

 
 
import java.util.Scanner;
 
	public class Project1 {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
 
		System.out.println("Enter the price of the house: ");
		double housePrice = input.nextDouble();
		System.out.println("Enter the down payment: ");
		double downPayment = input.nextDouble();
		System.out.println("Enter the annual interest rate: ");
		double annualInterestRate = input.nextDouble();
		System.out.println("Enter the number of payments: ");
		double numberofPayments = input.nextDouble();
 
 
		double tempTop = ((housePrice - downPayment) * (annualInterestRate/12));
		double tempBottom = ((1-(1+(Math.pow(annualInterestRate/12, -numberofPayments)))));
		double monthlyPayment = (tempTop / tempBottom);
		System.out.println( "The price of the house is: " + housePrice);
		System.out.println( "Your down payment is :" + downPayment);
		System.out.println( "Your annual interest rate is :" + annualInterestRate);
		System.out.println( "Your number of payments are :" + numberofPayments);		
		System.out.println( "Your monthly payment is :" + monthlyPayment);
		System.out.println( "");
		System.out.println( "Top of equation equals :" + tempTop);
 
		System.out.println( "Bottom of equation equals :" + tempBottom);	
 
 
	}	
	}

no

Originally Posted by iamgonge

double monthlyPayment= ( ((housePrice - downPayment) * (annualInterestRate/12)) /((1-(1+Math.pow(annualInterestRate/12, -numberofPayments)))));

Even try solving the problem, using a pen and paper. Make sure that its correct. For example :
housePrice = 30000.00
downPayment = 5000.00

then write it out like ( ((30000.00 - 50000.00) * ...

make sure you get the result you expect. Then compare this result with Java programs result.

ok i did the calculations on a calculator and they do equal each other, I bottom number keeps turning back a negative number which i dont think is right.

the formula im supposed to use is written on my paper like this PMT = (P - D)*r/12
__________
(1-(1+r/12)^-m) where P is the listed price of the house, D is the
down payment, r is the annual interest rate and m is the number of payments.

the bottom returns a negative which then turns the final number to a negative monthly payments cant be negative so something is wrong

PMT = (P - D)*r/12
______________
(1-(1+r/12)^-m)

Ok this is the formula. Do me a favour and post up what values you are using and the expected result.
Also annualInterestRate, is that a percentage % or a monetary value (£, $).