How biweekly savings are calculated
There are 52 weeks in a year, so paying every two weeks means 26 payments. Half a monthly payment 26 times equals 13 monthly payments — one more than the usual 12. We model this the way it works in practice: the extra is equivalent to adding one-twelfth of a payment to principal each month.
Biweekly payment = monthly payment ÷ 2
Extra per year = monthly payment (26 × ½ − 12)
Modelled as = monthly payment ÷ 12 added to principal every month
Worked example
$300,000 at 6.5% for 30 years:
| Monthly payment | $1,896.20 |
|---|---|
| Biweekly payment | $948.10 |
| Payoff, monthly | 30 years |
| Payoff, biweekly | 24 years 2 months |
| Interest saved | $87,259 |
Set it up without paying fees
Some third-party biweekly programs charge setup or per-payment fees and hold your money until a full payment is due. You get the same result for free by adding one-twelfth of your payment as extra principal each month, or by making one extra payment a year — try both in the mortgage payoff calculator. Ask your servicer how it applies partial payments before starting a biweekly schedule.
Frequently asked questions
Is biweekly the same as paying twice a month?
No. Twice a month is 24 half-payments, or exactly 12 full payments a year, which saves almost nothing. Biweekly is 26.
Does my lender have to accept biweekly payments?
Not necessarily. Many servicers hold partial payments until a full one is received. Paying extra principal monthly achieves the same effect.