A bi-weekly mortgage payment plan is a strategy where you pay half of your regular monthly mortgage payment every two weeks. Since there are 52 weeks in a year, this results in 26 half-payments, which is equivalent to 13 full monthly payments instead of the standard 12. This extra payment per year goes directly towards the principal balance, allowing you to pay off your mortgage faster and save a significant amount on interest over the life of the loan.
How the Bi-Weekly Mortgage Calculator Works
This calculator helps you understand the impact of a bi-weekly payment schedule on your mortgage. It takes into account the loan amount, the annual interest rate, and the loan term in years. By making these accelerated payments, you effectively reduce the loan's principal faster. The calculator determines:
The standard monthly payment.
The bi-weekly payment amount (half of the monthly payment plus any extra bi-weekly amount).
The total number of years and months it will take to pay off the mortgage with bi-weekly payments.
The total interest paid over the life of the loan with bi-weekly payments compared to a standard monthly payment schedule.
The total savings in interest and time.
The Math Behind the Calculation
The standard monthly mortgage payment (M) is calculated using the following formula:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
Where:
P = Principal Loan Amount
i = Monthly interest rate (Annual interest rate / 12)
n = Total number of payments (Loan term in years * 12)
For a bi-weekly payment, we first calculate the standard monthly payment (M) as above. Then, the bi-weekly payment (BW) is typically half of M, plus any additional extra bi-weekly payment specified. The core benefit of bi-weekly payments comes from making 13 full monthly payments (12 standard + 1 extra) per year, effectively making an extra monthly payment directly to the principal.
The calculator then simulates the amortization schedule with these accelerated payments to determine the new payoff timeline and total interest paid. It compares this to the original loan term and interest if only standard monthly payments were made.
Benefits of Bi-Weekly Payments
Accelerated Payoff: Significantly reduces the time it takes to own your home free and clear.
Interest Savings: By paying down principal faster, you pay less interest over the loan's lifetime.
Build Equity Faster: More of your payment goes towards ownership from the start.
Financial Discipline: Encourages consistent, slightly larger payments that can become a habit.
Considerations
While beneficial, ensure your lender supports bi-weekly payments directly. Some may charge fees, or you might need to set up automatic payments for half the monthly amount plus your extra bi-weekly contribution. If the lender doesn't offer a formal bi-weekly plan, you can often achieve similar results by manually making an extra principal payment equivalent to one monthly payment each year, or by simply increasing your regular monthly payment by 1/12th of your desired extra amount.
function calculateBiWeeklyMortgage() {
var principal = parseFloat(document.getElementById("loanAmount").value);
var annualRate = parseFloat(document.getElementById("annualInterestRate").value);
var years = parseFloat(document.getElementById("loanTermYears").value);
var extraBiWeekly = parseFloat(document.getElementById("extraPaymentBiWeekly").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(principal) || principal <= 0 ||
isNaN(annualRate) || annualRate <= 0 ||
isNaN(years) || years 0.01) { // Use a small tolerance for floating point comparisons
numPaymentsMade++;
simulatedMonths++;
var interestThisPeriod = remainingBalance * (annualRate / 100 / 26); // Bi-weekly interest calc based on 26 periods/year
remainingBalance -= totalBiWeeklyPayment – interestThisPeriod;
totalPaidBiWeekly += totalBiWeeklyPayment;
totalInterestPaid += interestThisPeriod;
// Prevent infinite loops in case of extreme values or calculation errors
if (numPaymentsMade > (years * 26 * 5) ) { // Safety break after 5x original term
resultDiv.innerHTML = "Calculation could not be completed. Please check your input values.";
return;
}
}
var actualPayoffYears = Math.floor((numPaymentsMade) / 26);
var actualPayoffMonths = Math.round((numPaymentsMade % 26) * (12/26)); // Approximate months
// Calculate standard loan payoff details for comparison
var standardTotalInterest = (standardMonthlyPayment * numMonthlyPayments) – principal;
var standardTotalCost = standardMonthlyPayment * numMonthlyPayments;
// Calculate savings
var interestSavings = standardTotalInterest – totalInterestPaid;
var timeSavingsYears = years – actualPayoffYears;
var timeSavingsMonths = 0;
// Calculate exact time savings in months more accurately
var originalTotalMonths = years * 12;
var calculatedTotalMonths = Math.round(numPaymentsMade * (12/26)); // Approximate months from bi-weekly payments
var exactTimeSavingsMonths = originalTotalMonths – calculatedTotalMonths;
if (exactTimeSavingsMonths < 0) exactTimeSavingsMonths = 0;
var finalPayoffYears = Math.floor(exactTimeSavingsMonths / 12);
var finalPayoffMonths = exactTimeSavingsMonths % 12;
var formattedStandardMonthlyPayment = standardMonthlyPayment.toFixed(2);
var formattedTotalBiWeeklyPayment = totalBiWeeklyPayment.toFixed(2);
var formattedPrincipal = principal.toFixed(2);
var formattedTotalInterestPaid = totalInterestPaid.toFixed(2);
var formattedInterestSavings = interestSavings.toFixed(2);
var formattedStandardTotalInterest = standardTotalInterest.toFixed(2);
var formattedTotalCostBiWeekly = (principal + totalInterestPaid).toFixed(2);
var formattedStandardTotalCost = standardTotalCost.toFixed(2);
resultDiv.innerHTML = `
Principal Loan Amount: $${formattedPrincipal}
Annual Interest Rate: ${annualRate.toFixed(2)}%
Original Loan Term: ${years} years
——————–
Standard Monthly Payment: $${formattedStandardMonthlyPayment}
Bi-Weekly Payment (incl. extra): $${formattedTotalBiWeeklyPayment}
——————–
New Payoff Time: ${actualPayoffYears} years and ${actualPayoffMonths} months
Total Interest Paid (Bi-Weekly): $${formattedTotalInterestPaid}
Total Cost (Bi-Weekly): $${formattedTotalCostBiWeekly}
——————–
Interest Savings: $${formattedInterestSavings}
Time Saved: ${finalPayoffYears} years and ${finalPayoffMonths} months
(Compared to standard ${years}-year term paying $${formattedStandardMonthlyPayment}/month)
`;
}