Whichever one you'll actually stick with. Both work by getting extra money to principal, and the gap between them is small enough that consistency beats mechanics. Bi-weekly payments have a slight mathematical edge. You end up making the equivalent of 13 monthly payments a year instead of 12, and because principal drops a little more often, the interest savings compound marginally faster. The catch: formal bi-weekly programs are largely a holdover from the days before online servicing, and some charge a setup or per-payment fee for something you can now do yourself for free. The simpler route, and the one we lean toward, is adding extra principal to your normal monthly payment. Most servicer portals let you set an additional-principal amount and change it anytime. Two easy versions: - Make one extra full payment a year, whenever it suits your cash flow. - Take one month's payment, divide it by 12, and add that slice to every month. Depending on your rate, one extra payment a year can shave several years off a 30-year loan, since more of every future payment then goes to principal. Run your numbers in an amortization calculator, pick how many years you want to cut, and set the auto-pay to hit it.