Biweekly Mortgage Calculator: How Much Do You Save vs Monthly?

How biweekly mortgage payments work

With a standard mortgage you make one payment a month, 12 times a year. On a biweekly plan you pay half of that monthly amount every 2 weeks instead. Paying every 2 weeks means 26 half-payments a year, which equals 13 full monthly payments. That one extra monthly payment each year goes toward principal, so the balance falls faster, less interest builds up, and the loan ends sooner.

There is a smaller second effect, too. When each half-payment is applied to the loan on the day it is received, the balance drops a little earlier in each cycle than it would with a single monthly payment, so slightly less interest accrues. Most of the benefit, though, comes from the extra payment, not from the timing.

Worked examples: biweekly vs. monthly

The table below shows three common loans run through this calculator. "Biweekly" here means true biweekly, with every payment applied when received.

Two patterns stand out. Larger balances and higher rates produce larger dollar savings, because there is more interest for the extra payment to avoid. Shorter terms save less, because a 15-year loan already carries much less interest to begin with. Run your own numbers in the calculator above.

True biweekly vs. the "13th payment" approach

Not every biweekly plan works the same way. Some servicers and third-party programs collect your half-payments every 2 weeks but hold the money and apply it once a month. The extra money then builds up and is credited once a year, which works much like making a single extra "13th" payment annually.

This approach still helps, but a little less. For the $300,000 example, the calculator's 13th-payment mode estimates $83,986.01 in interest saved and a payoff 5 years 8 months early, compared with $88,123.26 and 5 years 10 months for true biweekly.

The practical point: the bigger gap is not between these two methods. It is between paying the extra and not paying it. If your servicer won't apply half-payments as they arrive, making one extra payment a year on your own gets you close to the same result.

Who biweekly payments fit, and who should skip them

It may fit you if

• You are paid every 2 weeks and a half-payment lines up naturally with your paycheck.
• You plan to keep the home and the loan for many years, so the interest savings have time to build.
• Your servicer offers biweekly payments for free and applies each payment when it is received.

Consider skipping it, or adding extra principal instead, if

• The plan charges fees. Enrollment or per-payment processing fees eat directly into your savings. This calculator does not include any fees.
• Your servicer holds partial payments. Ask how half-payments are handled. If they sit in a suspense account until a full payment arrives, you are not getting true biweekly treatment.
• Your loan has a prepayment penalty. Check your loan documents or ask your servicer before paying ahead of schedule.
• Your cash flow is tight. An emergency fund or higher-interest debt, such as credit cards, may deserve the extra money first.
• You expect to sell or refinance soon. Most of the savings arrive in the later years of the loan.

Before you enroll anywhere, compare biweekly payments with simply adding extra principal to your regular monthly payment. Dividing one monthly payment by 12 and adding that amount each month produces a similar effect, usually with no enrollment and full control over when you stop. Check with your servicer that any extra is applied to principal and not to future payments.

Common pitfalls to avoid

• Paying for something you can do yourself. Some third-party biweekly services charge setup or recurring fees for a schedule you can often set up directly with your servicer, or replicate with extra principal payments.
• Assuming every plan is "true" biweekly. Get written confirmation of when payments are credited to the loan.
• Mislabeled extra money. If extra funds are treated as an early payment for next month instead of a principal reduction, you may not save interest. Check your statements.
• Forgetting the full housing payment. These estimates cover principal and interest only. Taxes, insurance, PMI, and HOA dues are separate and are not reduced by paying biweekly.

Methodology and assumptions

All results on this page are estimates, based on principal and interest only, true biweekly payments applied when received (unless you choose 13th-payment mode). The calculator uses these assumptions:

• Loan type: fixed-rate, fully amortizing. Property taxes, homeowners insurance, PMI, HOA dues, escrow, and biweekly program fees are not included.
• Monthly plan: interest at the annual rate ÷ 12, with the standard amortization formula and the payment rounded to the cent. The final payment is adjusted to clear the remaining balance.
• True biweekly (default): the payment is the monthly payment ÷ 2, rounded to the cent and paid every 14 days, 26 times a year. Interest accrues each period at the annual rate ÷ 26, and each payment is applied on the day it is received.
• 13th-payment mode: the loan keeps monthly amortization, and one extra full monthly payment is applied to principal once a year.
• Time saved: whole calendar months between the monthly and biweekly final payment dates, rounded down.
• Dates: the first payment defaults to the 1st of next month. Payment amounts and interest totals don't depend on the start date, but payoff dates shift with it.

Your servicer's actual figures may differ because of its posting rules, day-count method, escrow, and fees. Treat these results as a planning estimate, not a quote or financial advice.