Paying your mortgage every two weeks instead of once a month sounds like a trivial scheduling tweak. It is not. Because there are 26 biweekly periods in a year, half-payments add up to 13 full monthly payments instead of 12 — one extra payment a year that goes straight at your principal. This calculator contrasts the standard monthly plan with the biweekly plan on the same Loan Amount, Annual Interest Rate, and Loan Term (Years), showing the Bi-Weekly Payment, the interest under each schedule, and the years you shave off.

Take a $300,000 loan at 6.5% over 30 years. The standard Monthly Payment is about $1,896. Paying half of that — roughly $948 — every two weeks cuts total interest by around a quarter and can erase roughly six years from the loan. The Interest Saved figure often lands in the tens of thousands of dollars, which is why lenders market biweekly programs so aggressively.

One caution: some lenders charge setup fees for biweekly plans or simply hold your extra half-payment until month-end. You can get the same effect free by adding one-twelfth of your payment to each monthly check.

With the pre-filled defaults — Loan Amount $300,000, Annual Interest Rate 6.5%, Loan Term (Years) 30 — the Bi-weekly Payment Calculator returns Monthly Payment $1,896.20, Bi-Weekly Payment $948.10, Total Interest (Monthly) $382,633.47, Total Interest (Bi-Weekly) $286,975.10, Interest Saved $95,658.37, Years Saved 5.7. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.