Biweekly Mortgage Calculator
Half a payment every two weeks quietly makes thirteen full payments a year. See how many years that knocks off your mortgage and how much interest it saves.
The thirteenth payment hiding in the calendar
There are 26 two-week periods in a year, so 26 half-payments equal 13 full monthly payments — one whole extra payment annually, aimed entirely at principal after interest. No pay rise required; the calendar does it. The debate is only whether your servicer applies it that way.
26 biweekly half-payments = 13 monthly payments per year
Example: $300,000 at 6% over 30 years. Monthly: $1,798.65, total interest $347,515. Biweekly halves of $899.33: the loan clears in about 24.5 years and saves roughly $70,000 of interest. The calculator below runs your exact figures.
The servicer caveat
Some servicers hold partial payments until the second half arrives, which quietly deletes the benefit; others charge a fee for a 'biweekly program' that replicates what a calendar does free. Check that each half-payment is credited on receipt — or simply send one extra monthly payment's worth across the year yourself and keep every cent of the effect.
How this is calculated
The biweekly run simulates 26 periods a year at the nominal rate ÷ 26, each payment exactly half the standard monthly payment (computed at rate ÷ 12 over the term in months). The comparison is the standard amortization. Actual payoff period counts come from the simulation, not a closed-form estimate, and the interest figures are summed period by period.
Frequently asked questions
Is biweekly the same as paying twice a month?
No — twice a month is 24 half-payments, exactly 12 monthly payments, and saves almost nothing. Every two weeks is 26 half-payments: the extra two halves are the entire trick.
Can I do this without a formal program?
Yes. Divide your monthly payment by 12 and add that amount as extra principal to every normal payment — the yearly total matches the biweekly effect almost exactly, with no fees and no servicer cooperation needed.
Why do some lenders charge for biweekly programs?
Because they can. Third-party programs have historically charged setup and per-payment fees to administer a schedule you can replicate yourself with a standing extra-principal instruction.
Does biweekly help on a 15-year loan as much?
Proportionally less: shorter terms carry less total interest, so there is less to save. The mechanism is identical; run your figures above.
Embed this calculator
Writing about money — a blog, a school page, a community site? Put this calculator on your page, free: copy the code below and paste it where you want the calculator to appear. It stays up to date automatically — the small credit line underneath is all we ask in return.
CalcPrincipal