Put both options on the same annual budget
Do not compare a 12-payment schedule with a 13-payment schedule without showing the extra annual cash. Convert both strategies into total dollars paid each year before comparing savings.
Monthly extra principal is often easier to control
Adding one-twelfth of a monthly payment to each regular payment can approximate one extra payment per year. It can also be paused when cash flow is tight, provided the lender applies it correctly.
Verify the servicing details before enrolling
Some third-party biweekly programs hold funds or charge fees. Ask when each payment is credited, whether partial payments are held, and how to mark additional principal.
Test your scenario
Use the related calculators
The guide frames the comparison; the calculators let you enter your own numbers and test alternatives.