Mortgage Amortization Calculator Extra Payments

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Mortgage Repayment Calculator

Estimate your monthly payments and total interest costs.

Monthly Principal & Interest:
Total Loan Amount:
Total Interest Paid:
Total Cost of Loan:

How to Use This Mortgage Calculator

Buying a home is one of the most significant financial decisions you will ever make. Our Mortgage Repayment Calculator helps you understand the long-term financial commitment by breaking down your monthly obligations. To get an accurate estimate, you need four key pieces of information: the total purchase price, your cash down payment, the annual interest rate offered by your lender, and the length of the loan (usually 15 or 30 years).

Understanding the Calculation

The core of this tool uses the standard amortization formula to determine your fixed monthly payment. The formula used is:

M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]

  • M: Total monthly payment.
  • P: Principal loan amount (Home Price – Down Payment).
  • i: Monthly interest rate (Annual Rate / 12 months).
  • n: Number of months (Years x 12).

Real-World Example

Let's look at a realistic scenario for a first-time homebuyer:

  • Home Price: $400,000
  • Down Payment: $80,000 (20%)
  • Interest Rate: 7.0%
  • Loan Term: 30 Years

In this example, the loan principal is $320,000. Using the formula, the monthly principal and interest payment would be approximately $2,128.98. Over 30 years, the total interest paid would amount to $446,432.80, making the total cost of the loan $766,432.80.

Key Factors That Influence Your Payment

1. Down Payment: A larger down payment reduces your loan principal, which directly lowers your monthly payment and the total interest paid over time. If you put down less than 20%, you may also need to factor in Private Mortgage Insurance (PMI).

2. Credit Score: Lenders use your credit score to determine your interest rate. Even a 0.5% difference in your rate can save or cost you tens of thousands of dollars over the life of the loan.

3. Loan Term: A 15-year mortgage usually has a lower interest rate but higher monthly payments compared to a 30-year mortgage. However, you will pay significantly less in total interest with a shorter term.

function calculateMortgage() { var homePrice = parseFloat(document.getElementById("homePrice").value); var downPayment = parseFloat(document.getElementById("downPayment").value); var interestRate = parseFloat(document.getElementById("interestRate").value); var loanTerm = parseFloat(document.getElementById("loanTerm").value); if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || homePrice <= 0) { alert("Please enter valid positive numbers for all fields."); return; } var principal = homePrice – downPayment; if (principal <= 0) { alert("Down payment cannot be equal to or greater than the home price."); return; } var monthlyInterest = (interestRate / 100) / 12; var numberOfPayments = loanTerm * 12; // Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ] var x = Math.pow(1 + monthlyInterest, numberOfPayments); var monthlyPayment = (principal * x * monthlyInterest) / (x – 1); var totalCost = monthlyPayment * numberOfPayments; var totalInterest = totalCost – principal; // Formatting currency var formatter = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD', }); document.getElementById("resMonthly").innerHTML = formatter.format(monthlyPayment); document.getElementById("resLoanAmount").innerHTML = formatter.format(principal); document.getElementById("resTotalInterest").innerHTML = formatter.format(totalInterest); document.getElementById("resTotalCost").innerHTML = formatter.format(totalCost); document.getElementById("mortgage-results").style.display = "block"; }

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