Biweekly Mortgage Calculator
One Extra Payment a Year, Almost by Accident
Switching from monthly to biweekly mortgage payments feels like a scheduling change, but it quietly changes the math. Paying half the monthly payment every two weeks means 26 half-payments a year — the equivalent of 13 full monthly payments instead of 12. That extra payment goes straight to principal, and because it happens automatically rather than requiring a separate decision each year, it's one of the more painless ways to shorten a mortgage.
The Formula
The calculator amortizes the loan under this biweekly schedule, applying the biweekly interest rate to the declining balance each period, and compares the resulting payoff time and total interest against the standard monthly schedule.
Where This Calculation Matters
- Shortening a mortgage without refinancing — no new loan, no closing costs, just a change in payment frequency that many lenders and servicers support directly.
- Interest savings compound with loan size — the extra annual payment has a bigger absolute dollar impact on larger loans and higher rates.
- Aligning payments with biweekly paychecks — for borrowers already paid every two weeks, this schedule can be easier to budget against than a monthly lump sum.
- Comparing against lump-sum prepayment — biweekly payments produce steady, automatic acceleration, versus the extra-payment approach that requires an active monthly decision.
A Worked Example
A $300,000 loan at 6.5% over a standard 30-year term:
| Schedule | Payoff time | Total interest |
|---|---|---|
| Standard monthly | 30.0 years | $382,633.47 |
| Biweekly | 24.2 years | $294,511.68 |
| Savings | 5.8 years faster | $88,121.78 less interest |
How to Use This Calculator
- Enter the Loan Amount, Interest Rate, and Loan Term (years) from your current or planned mortgage.
- Select Calculate to see the biweekly payoff timeline compared against the standard monthly schedule, including total interest paid under each and the time and interest saved.
Related Calculations
Compare this against making one large extra payment instead with the Extra Mortgage Payment Calculator, or see how the standard schedule alone plays out with the Affordability Calculator.