Biweekly Mortgage Calculator (13 Payments a Year)
Enter your loan amount, rate, and term to compare a standard monthly schedule against half-payments every two weeks: total interest on each plan, the years you'd shave off, and where the hidden 13th payment comes from.
The balance the schedule starts from
The annual rate on your mortgage
The term the monthly plan is written for
Biweekly payment
$948
half the $1,896 monthly payment, 26 times a year
Interest saved
$88,122
$294,512 biweekly vs $382,633 monthly
Paid off sooner by
5 years 10 months
done in about 24.2 years instead of 30
Monthly plan vs. accelerated biweekly
| Plan | Payment | Paid per year | Payoff time | Total interest |
|---|---|---|---|---|
| Monthly (12 payments) | $1,896 | $22,754 | 30 years | $382,633 |
| Biweekly (26 half-payments) | $948 | $24,651 | 24.2 years | $294,512 |
26 half-payments equal 13 full payments a year; the 13th goes straight to principal. Interest timing varies by servicer, so treat these as close estimates rather than to-the-dollar quotes.
The 13th payment, hiding in the calendar
The biweekly trick is calendar arithmetic. A year holds 52 weeks, which is 26 two-week periods, but only 12 months. Pay half your mortgage payment every two weeks and you make 26 half-payments: 13 full payments instead of 12. Nobody feels the 13th because it arrives as small, regular slices synced to a biweekly paycheck, but the loan feels it: one entire payment of extra principal every year, plus a small bonus from each half-payment landing earlier than the monthly version would. The result bends the whole amortization curve downward.
What it does to a $300,000 loan
Take the calculator's defaults: $300,000 at 6.5% for 30 years. The monthly plan costs about $1,896 a month and roughly $383,000 in total interest. Switch to $948 every two weeks and the loan ends in about 24 years instead of 30, with total interest near $295,000: close to $88,000 saved and almost six years returned, without any single moment where the budget felt different. The per-year outlay rises by exactly one payment, from about $22,750 to $24,650, which is the honest price of the whole effect. The amortization calculator shows the same loan year by year if you want to watch the balance column fall.
Choosing between biweekly and a plain extra payment
Biweekly shines when your income is biweekly: 26 paychecks map cleanly onto 26 half-payments, and the plan runs itself. If you're paid monthly, or your servicer holds half-payments until both halves arrive, the simpler route is the same math in different clothes: add one twelfth of your payment to each month as extra principal, or make one extra payment a year. The mortgage payoff calculator lets you test any extra amount, not just the built-in 13th payment. Either way, confirm extras are applied to principal, and treat paid biweekly programs with suspicion: the calendar does this work for free. Whether those freed-up years are better spent invested is a fair question, and our save-or-invest guide frames the trade.
Frequently asked questions
How do biweekly payments save money?
There are 26 two-week periods in a year, so paying half your mortgage payment every two weeks adds up to 13 full payments instead of 12. That extra payment goes entirely to principal, and each payment lands a little earlier than its monthly counterpart, so interest accrues on a smaller balance. On a typical 30-year loan the combination removes several years and tens of thousands in interest.
Is biweekly the same as paying twice a month?
No, and the difference is the whole trick. Semi-monthly means 24 half-payments a year, which is exactly 12 full payments: no extra principal. Biweekly means 26 half-payments, which is 13 full payments. Only the biweekly schedule sneaks in the extra one.
Do all mortgage servicers support biweekly payments?
No. Some apply each half-payment as it arrives, some hold the first half until the second lands, and some only accept the arrangement through a paid program. Holding the halves cancels the early-payment benefit but keeps the 13th-payment benefit, which is most of the savings. Ask your servicer how partial payments are applied before you set anything up.
Can I get the same effect without changing my schedule?
Yes. Divide your monthly payment by 12 and add that amount to each month's payment as extra principal. That reproduces the 13th payment without touching your payment schedule or relying on your servicer's handling of half-payments. One extra full payment each year works too.
Should I pay a fee for a biweekly payment program?
Usually not. The math a paid program sells is the same math you can run for free by sending one extra payment a year or a twelfth extra each month, marked as principal. A setup or per-payment fee just subtracts from savings you could have kept.
Does this calculator save my numbers?
No. Everything runs in your browser and nothing you type is stored or sent anywhere.
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