Prejudgment Interest Calculator Texas

Mortgage Principal & Interest Calculator

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function calculateMortgagePayment() { // Get input values var homePriceStr = document.getElementById('mc_homePrice').value; var downPaymentStr = document.getElementById('mc_downPayment').value; var loanTermStr = document.getElementById('mc_loanTerm').value; var interestRateStr = document.getElementById('mc_interestRate').value; // Parse values to floats var homePrice = parseFloat(homePriceStr); var downPayment = parseFloat(downPaymentStr); var loanTermYears = parseFloat(loanTermStr); var annualRatePercent = parseFloat(interestRateStr); // Helper function for currency formatting function formatCurrency(num) { return num.toLocaleString('en-US', { style: 'currency', currency: 'USD' }); } var resultDiv = document.getElementById('mc_resultOutput'); // Basic Validation if (isNaN(homePrice) || isNaN(downPayment) || isNaN(loanTermYears) || isNaN(annualRatePercent)) { resultDiv.innerHTML = 'Please fill in all fields with valid numbers.'; return; } if (homePrice <= 0 || loanTermYears <= 0 || annualRatePercent < 0 || downPayment < 0) { resultDiv.innerHTML = 'Please enter positive values. Interest rate cannot be negative.'; return; } // Calculate Principal Amount var principal = homePrice – downPayment; if (principal <= 0) { resultDiv.innerHTML = 'Your down payment equals or exceeds the home price. You do not need a mortgage.'; return; } // Mortgage Calculation Variables var monthlyRate = (annualRatePercent / 100) / 12; var numberOfPayments = loanTermYears * 12; var monthlyPayment = 0; // Handle zero interest rate edge case if (monthlyRate === 0) { monthlyPayment = principal / numberOfPayments; } else { // Standard Mortgage Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ] var numerator = monthlyRate * Math.pow((1 + monthlyRate), numberOfPayments); var denominator = Math.pow((1 + monthlyRate), numberOfPayments) – 1; monthlyPayment = principal * (numerator / denominator); } // Summary Calculations var totalPayback = monthlyPayment * numberOfPayments; var totalInterest = totalPayback – principal; // Generate Output HTML var outputHTML = ''; outputHTML += '

'; outputHTML += '

Estimated Monthly Payment

'; outputHTML += " + formatCurrency(monthlyPayment) + "; outputHTML += '(Principal & Interest Only)'; outputHTML += '

'; outputHTML += '

'; outputHTML += 'Loan Principal: ' + formatCurrency(principal) + "; outputHTML += 'Total Interest Paid: ' + formatCurrency(totalInterest) + "; outputHTML += 'Total Cost of Loan: ' + formatCurrency(totalPayback) + "; outputHTML += '

'; resultDiv.innerHTML = outputHTML; }

Understanding Your Mortgage Payment

Buying a home is likely the largest purchase you will ever make, and understanding how your financing works is crucial to maintaining financial health. This Mortgage Principal & Interest Calculator is designed to help prospective homeowners estimate their monthly housing costs based on current market rates and their budget.

It is important to note that the figure calculated above represents only the Principal and Interest (P&I) portion of your payment. Your actual monthly obligation to your lender will likely be higher, as it often includes escrow payments for property taxes, homeowners insurance, and potentially Private Mortgage Insurance (PMI) if your down payment is less than 20%.

How the Mortgage Calculation Works

The core of a fixed-rate mortgage calculation relies on four key inputs:

• Home Price: The final agreed-upon sale price of the property.
• Down Payment: The upfront cash you pay toward the home price. The remaining balance forms your loan principal.
• Loan Term: The duration over which you agree to repay the loan. The most common terms are 30 years and 15 years. A longer term means lower monthly payments but significantly more interest paid over time.
• Interest Rate: The annual cost of borrowing money, expressed as a percentage. Even a small fraction of a percentage point difference in rate can impact your monthly payment by hundreds of dollars.

The Impact of Interest: An Example

Understanding how interest accumulates is vital. In the early years of a standard 30-year mortgage, the vast majority of your monthly payment goes toward paying off interest, not the principal balance.

For example, consider a $450,000 home with a $90,000 (20%) down payment, leaving a loan amount of $360,000. If you secure a 30-year fixed-rate mortgage at 6.5%:

• Your estimated monthly P&I payment would be roughly $2,275.
• Over the 30-year life of the loan, you would pay approximately $459,000 just in interest—more than the original loan amount itself.

Using this calculator allows you to adjust these variables to see how increasing your down payment, shopping for a lower rate, or choosing a shorter loan term can save you money in the long run.