Biweekly Mortgage Calculator

How "half every two weeks" beats "once a month"

The trick hiding inside a biweekly mortgage is a calendar quirk. If you pay half your monthly mortgage every two weeks, you make 26 half-payments a year — which equals 13 full monthly payments instead of 12. That one extra payment slips in almost painlessly, but because it goes entirely toward principal, it attacks the part of your loan that's generating interest. On a typical 30-year mortgage, that single bonus payment each year can shorten the loan by roughly four to six years and save tens of thousands of dollars in interest. This calculator runs both schedules and shows you the gap.

Why does such a small change do so much? Mortgages are front-loaded with interest — in the early years, most of your payment covers interest and only a sliver touches principal. Every extra dollar of principal you pay early permanently removes the interest that dollar would have generated for the rest of the loan. By chipping in an extra payment annually and paying slightly more often, you accelerate the balance downward, which compounds into large savings over decades. The effect is strongest on long terms and higher rates, which is exactly when interest is the most punishing.

A couple of practical cautions. First, check that your lender applies biweekly payments to principal immediately rather than holding them until a full monthly payment accumulates — if they just hold the money, you lose most of the benefit. Second, beware third-party "biweekly enrollment" services that charge setup and per-payment fees for something you can usually do yourself for free. The simplest do-it-yourself version is to keep paying monthly but add one-twelfth of a payment to each month, or make one extra payment a year — you capture nearly the same savings with zero fees and full flexibility to skip it in a tight month.