How Biweekly Payments Work

A standard mortgage requires one payment per month, for a total of twelve payments each year. With a biweekly plan, you split the monthly payment in half and pay that amount every two weeks. Because there are 52 weeks in a year, this schedule results in 26 half-payments, which equals 13 full payments annually—one extra compared to the conventional approach. That seemingly small change reduces principal faster, decreasing the total interest paid and shortening the payoff period. This calculator contrasts the two methods so you can decide whether switching to biweekly payments fits your financial goals.

The first step is to compute the regular monthly payment using the familiar amortization formula. If represents the loan principal, is the monthly interest rate, and is the total number of monthly payments, then the payment amount is given by

Most lenders derive this equation from the concept of the present value of an annuity. Once you know the monthly payment, the biweekly payment is simply half that amount. The real magic comes from applying that payment every two weeks. Interest accrues more frequently—every half month—so the calculator simulates the payoff by iterating through each period, adding interest, subtracting the payment, and counting how many periods it takes to eliminate the balance. Because there are 26 periods per year, the balance declines faster than under the monthly schedule.

The table below illustrates the impact for a $300,000 loan at 6% interest over 30 years. The biweekly plan saves tens of thousands of dollars and cuts years off the loan:

Payment Plan	Total Interest	Years to Payoff
Monthly	$347,515	30
Biweekly	$304,878	25.4

These figures come from applying the formulas outlined above. The monthly payment for this loan is roughly $1,799. With a biweekly schedule, you pay about $900 every two weeks. Over the course of a year, you end up contributing an extra $1,799, all of which goes toward principal because it is above the amortized requirement. By reducing principal sooner, subsequent interest charges are calculated on a smaller balance, creating a snowball effect that accelerates payoff.

Switching to biweekly payments can also have behavioral benefits. Many people receive paychecks every two weeks, so aligning mortgage payments with pay periods simplifies budgeting. The half-payment size may feel more manageable, even though you ultimately pay slightly more each year. Some lenders offer official biweekly programs that automatically draft payments and forward them to the servicer. These programs may charge fees, so weigh the convenience against any costs. Alternatively, you can mimic a biweekly plan on your own by adding one extra monthly payment per year or by making principal-only payments whenever you have surplus cash.

Before enrolling in a biweekly plan, confirm that your lender applies extra payments directly to principal and does not hold them in suspense. A payment held in suspense earns no interest reduction until enough funds accumulate to cover a full monthly payment. This calculator assumes each biweekly payment is applied immediately, which maximizes savings. If your lender handles extra payments differently, the benefits may diminish.

It is also important to consider opportunity cost. The extra payment you make each year could alternatively be invested elsewhere, potentially earning a higher return. If your mortgage rate is relatively low and you can confidently earn more in investments, accelerating mortgage payoff may not be the optimal use of funds. On the other hand, the guaranteed interest savings from biweekly payments can be appealing to those who value debt-free living and risk reduction.

The calculator allows you to experiment with different loan amounts, terms, and rates. Try entering a shorter term or a higher interest rate to see how the biweekly plan's advantage changes. At very low rates or short terms, the interest savings shrink, but the psychological benefit of finishing early might still be worthwhile. Conversely, for long-term loans at moderate rates, the savings can be substantial, making the biweekly approach a compelling strategy.

Ultimately, a biweekly mortgage payment plan is a simple yet powerful tool. By turning the calendar to your advantage, you effectively sneak in an extra payment each year without significantly increasing your monthly budget. Use this calculator to understand the mechanics and to quantify the potential benefits. Armed with that knowledge, you can decide whether the accelerated path aligns with your broader financial objectives.