function calculateRefi() {
var balance = parseFloat(document.getElementById('loanBalance').value);
var costs = parseFloat(document.getElementById('closingCosts').value);
var currentRate = parseFloat(document.getElementById('currentRate').value) / 100 / 12;
var newRate = parseFloat(document.getElementById('newRate').value) / 100 / 12;
var termMonths = parseFloat(document.getElementById('loanTerm').value) * 12;
if (isNaN(balance) || isNaN(costs) || isNaN(currentRate) || isNaN(newRate) || balance <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
// Calculate Monthly Payments (P * r * (1+r)^n) / ((1+r)^n – 1)
var currentPayment = (balance * currentRate * Math.pow(1 + currentRate, termMonths)) / (Math.pow(1 + currentRate, termMonths) – 1);
var newPayment = (balance * newRate * Math.pow(1 + newRate, termMonths)) / (Math.pow(1 + newRate, termMonths) – 1);
var savings = currentPayment – newPayment;
var resultsDiv = document.getElementById('refi-results');
var savingsSpan = document.getElementById('monthlySavings');
var breakEvenSpan = document.getElementById('breakEvenTime');
var analysisP = document.getElementById('refi-analysis');
resultsDiv.style.display = 'block';
if (savings <= 0) {
savingsSpan.innerText = "$0.00";
breakEvenSpan.innerText = "Never";
savingsSpan.style.color = "#e74c3c";
analysisP.innerHTML = "Warning: Your new monthly payment is higher than or equal to your current payment. Refinancing at these rates may not be financially beneficial unless you are significantly shortening your loan term.";
} else {
var breakEvenMonths = costs / savings;
var years = Math.floor(breakEvenMonths / 12);
var remainingMonths = Math.ceil(breakEvenMonths % 12);
savingsSpan.innerText = "$" + savings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
savingsSpan.style.color = "#27ae60";
var timeString = "";
if (years > 0) {
timeString += years + (years === 1 ? " Year " : " Years ");
}
timeString += remainingMonths + (remainingMonths === 1 ? " Month" : " Months");
breakEvenSpan.innerText = timeString;
analysisP.innerHTML = "By refinancing, you will save $" + savings.toFixed(2) + " per month. It will take " + timeString + " to recover your closing costs of $" + costs.toLocaleString() + ". If you plan to stay in your home longer than this period, refinancing is likely a strong financial move.";
}
}
Understanding Your Refinance Break-Even Point
When you refinance your mortgage, you are essentially replacing your current loan with a new one, typically to secure a lower interest rate or change the loan term. However, refinancing isn't free. You must pay closing costs, which usually range from 2% to 5% of the loan amount.
What is a "Break-Even Point"?
The break-even point is the specific moment in time when the monthly savings generated by your lower interest rate equal the total cost of the refinance. Before this point, you are technically at a loss. After this point, the monthly savings are "pure profit" that stay in your pocket.
The Break-Even Formula
Total Closing Costs ÷ Monthly Savings = Months to Break Even
Example Calculation
Current Balance: $300,000
Refinance Costs: $6,000
Current Payment: $2,100
New Payment: $1,850
Monthly Savings: $250
Break-Even: $6,000 ÷ $250 = 24 Months (2 Years)
Factors to Consider
When using this calculator, keep the following variables in mind:
Duration of Residency: If your break-even point is 5 years but you plan to sell the house in 3 years, refinancing will actually cost you money.
Loan Term Reset: If you have 20 years left on a 30-year mortgage and refinance into a new 30-year mortgage, you may lower your monthly payment but pay significantly more in interest over the life of the loan.
Tax Implications: Mortgage interest is often tax-deductible. A lower interest rate might slightly reduce your tax deduction, though the direct savings usually outweigh this.
Opportunity Cost: Consider what you could do with the money spent on closing costs if you invested it elsewhere instead of paying for the refinance.