Biweekly Mortgage Payment Calculator for an Existing Mortgage
Already have a mortgage? Switching to biweekly payments adds one extra payment a year. See the interest and time it saves on your remaining balance.
A worked example
Running this tool on current national benchmarks (Federal Reserve / Freddie Mac via FRED (St. Louis Fed)) — swap in your own numbers to see how the result moves.
- Current balance
- $240,000
- Interest rate
- 6.50%
- Years remaining
- 25
paid off 4.2 years sooner
- Monthly payment$1,620.50
- Biweekly payment$810.25
- New payoff20.8 yrs
How the interest saved with biweekly changes with current balance
Holding the other inputs at the example above, here is how the result moves as current balance changes.
| Current balance | Interest saved with biweekly | Monthly payment |
|---|---|---|
| $150,000 | $30,235 | $1,012.81 |
| $250,000 | $50,392 | $1,688.02 |
| $400,000 | $80,627 | $2,700.83 |
| $600,000 | $120,940 | $4,051.24 |
The math behind it
This version works from your current balance and the years you have left rather than a new loan. It finds the monthly payment that would pay off your remaining balance over that time, halves it, and applies that half every two weeks — 26 payments a year, the equivalent of 13 monthly ones. It then compares how much sooner your loan is gone and how much interest you save against continuing to pay monthly.
Assumptions & limits
- The calculation starts from your remaining balance and remaining term, not the original loan. Interest accrues biweekly at the rate divided by 26.
- The rate is fixed for the rest of the term. Payments are principal and interest only — taxes and insurance are excluded.
- It assumes the half-payments are credited to principal as they arrive; a servicer that holds them removes the benefit.
- No program or transaction fees are included.
Source: Freddie Mac PMMS via FRED. Annual averages; latest weekly reading shown.
Common questions
Does switching to biweekly work on a loan I already have?
Yes. The extra-payment effect applies to any remaining balance. Switching part-way through still adds the equivalent of one extra payment a year, saving interest and shaving time off whatever term you have left — the earlier you switch, the more you save.
Should I check anything with my servicer first?
Confirm two things: that they accept biweekly payments and apply each half immediately, and that there is no prepayment penalty. Some servicers hold half-payments until a full one accumulates, which cancels the benefit. If so, make a monthly payment plus extra principal instead.
Is biweekly better than just refinancing to a shorter term?
They solve different problems. Switching to biweekly accelerates payoff at your current rate with no closing costs. Refinancing to a shorter term can cut the rate too, but carries fees and a locked higher payment. If your rate is already low, biweekly payments are the cheaper way to pay off faster.