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Biweekly Mortgage Calculator
Use this free biweekly mortgage calculator to see what paying half your mortgage every two weeks really does. Enter your loan amount, rate, and term, and it works out the monthly payment, the biweekly payment, how much sooner the loan is paid off, and exactly how much interest you save compared with a normal monthly schedule. The payoff chart shows the balance falling faster year by year.
Added to each half-payment to pay off faster.
Both options pay 13 monthly payments a year. The monthly version is easier if your lender does not accept biweekly payments.
How it works
A biweekly mortgage is not a different loan and it does not change your interest rate. It only changes when the money goes in. Instead of one full payment each month, you pay half the monthly amount every two weeks. A year has 52 weeks, so there are 26 two-week periods — and 26 half-payments add up to 13 full monthly payments a year instead of 12. That one extra payment a year is the entire trick, and it is a powerful one, because every dollar of it goes toward the principal.
First the calculator finds the standard monthly payment from the usual amortization formula, using the monthly rate (annual rate divided by 12) and the total number of monthly payments. On a $300,000 loan at 6 percent over 30 years, that is $1,798.65 a month. The biweekly payment is half of that: $899.33 every two weeks. Then it simulates the loan period by period, charging interest at the annual rate divided by 26 for each two-week period and subtracting the payment, until the balance reaches zero. The monthly comparison is simulated the same way, one payment a month for the full term.
Why does one extra payment a year save so much? Interest is charged on the balance, so anything that cuts the balance early cuts every interest charge after it. The extra payment lands in the months when the calendar gives you three biweekly paydays instead of two, and it reduces the balance months or years before it would otherwise have fallen. That is also why the saving is biggest on long, high-rate loans: a 30-year loan at 6 percent spends years with a large balance, so early principal cuts have decades to compound. On a 15-year loan at 3 percent the saving is far smaller, though still real.
The "Monthly + 1/12 extra" option produces almost the same result without a biweekly program. You add one-twelfth of the monthly payment — $149.89 on the example loan — to each monthly payment, so over a year you have paid the same 13 monthly payments. Some lenders do not accept biweekly payments, or charge for the service, so this version is often the practical choice. The numbers differ by a few dollars because biweekly payments also arrive slightly earlier in the year, but the payoff time and saving are within a month and a few hundred dollars of each other.
Adding an extra amount to each biweekly payment speeds things up further, and the calculator lets you test that too. An extra $50 per biweekly payment is $1,300 a year of additional principal, which on the example loan cuts roughly another two and a half years off the payoff. But before committing to any accelerated schedule, keep two checks in mind. First, make sure the lender applies extra money to principal rather than holding it as a future payment. Second, keep an emergency fund: money sent to the mortgage is hard to get back, and a biweekly schedule is harder to pause than a single extra payment made when you can afford it.
Worked example
A $300,000 mortgage at 6 percent annual interest over 30 years, paid biweekly with no extra payment.
Step 1: Monthly payment — $300,000 × (0.06 ÷ 12) ÷ (1 − (1 + 0.06 ÷ 12)−360) = $1,798.65.
Step 2: Biweekly payment — $1,798.65 ÷ 2 = $899.33 every two weeks.
Step 3: Payoff — simulating 26 payments a year at the biweekly rate, the balance reaches zero after 638 payments, which is 24 years 6 months instead of 30 years.
Step 4: Total interest, monthly schedule — $1,798.65 × 360 − $300,000 = $347,514.57.
Step 5: Total interest, biweekly schedule — $273,078.55.
Step 6: Interest saved — $347,514.57 − $273,078.55 = $74,436.02.
Enter the same numbers in the calculator and it gives exactly the same result: monthly $1,798.65, biweekly $899.33, payoff in 24 years 6 months, and $74,436.02 of interest saved. Try adding $100 of extra payment per biweekly payment and watch the payoff time fall by more than another year.
FAQ
How does a biweekly mortgage payment work?
You pay half of your normal monthly mortgage payment every two weeks instead of the full payment once a month. Because there are 26 two-week periods in a year, you make 26 half-payments, which adds up to 13 full monthly payments a year instead of 12. That one extra payment each year goes straight toward the principal, so the loan is paid off years earlier and you pay much less interest.
How much does a biweekly mortgage save?
On a $300,000 loan at 6 percent over 30 years, the monthly payment is $1,798.65 and the total interest on a monthly schedule is $347,514.57. Paying $899.33 every two weeks pays the loan off in about 24 years 6 months, with total interest of $273,078.55 — a saving of about $74,436. The saving grows with higher rates and longer terms, and shrinks when rates are low.
Is biweekly the same as semi-monthly?
No. Biweekly means every two weeks, which is 26 payments a year. Semi-monthly means twice a month, which is 24 payments a year — the same total as 12 monthly payments, so it saves nothing. The whole benefit of biweekly payments comes from the 26th and 27th half-payments that add up to one extra monthly payment per year.
Do all lenders offer biweekly payments?
No, not all lenders accept biweekly payments directly, and some charge a setup fee or a small fee per payment for a biweekly program. Many borrowers get the same result without a program by adding one-twelfth of the monthly payment to each monthly payment, or by making one extra monthly payment a year. Check whether your lender applies extra money to principal, and whether there is a prepayment penalty, before you start.
Can I switch back to monthly payments later?
Usually yes, if you are paying biweekly on your own by adding extra to each monthly payment — you simply stop adding the extra. If you joined a formal biweekly program run by your lender or a third party, the terms of that program decide how and when you can leave, and some charge a fee to cancel. Keep an emergency fund first: the extra payment each year is real money leaving your account, and a biweekly schedule is harder to pause than a single extra payment.