About this calculator
There are 52 weeks in a year, so paying every two weeks means 26 half-payments — the equivalent of 13 full monthly payments, not 12. That extra payment is the entire trick: it lands on principal, the balance falls faster every period after it, and because interest is charged on the balance, each subsequent payment carries less interest and more principal. Nothing about the rate or the loan changes; only the calendar does.
On a $320,000 loan at 6.5% over 30 years, the biweekly schedule finishes in about 24 years 2 months instead of 30 — roughly 5.9 years sooner — and saves about $94,000 of interest. The effect is bigger at higher rates and longer terms, and smaller (but still real) on 15-year loans. One honest caveat: many servicers do not accept partial payments. The widely sold workaround — servicer-run "biweekly programs" that draft half-payments, hold them, and remit monthly — delays the extra principal and often carries a setup fee plus monthly fees. You can reproduce the true effect yourself, free, by paying one extra monthly payment a year (or 1/12 extra each month) marked "apply to principal" — this calculator tells you exactly what that discipline is worth on your loan.
How to use it
- Enter your loan amount, rate and term — the same inputs as a standard mortgage calculation.
- Read the biweekly payment (half the monthly figure) and the interest saved against paying monthly.
- Check the year-by-year table: the biweekly balance pulls away from the monthly balance a little more each year.
- If your servicer offers a biweekly program, compare its fees against the interest saved here — and ask whether payments are applied on receipt or held.
The formula
The loan is re-amortized on a two-week clock. Because 26 half-payments exceed 24, one extra monthly payment a year reaches the principal; the simulation above simply steps the balance period by period until it reaches zero, which is why the payoff count (628 periods on the example loan) and the interest total are exact for the stated schedule.
Worked example
A $320,000 loan at 6.5% for 30 years costs $2,022.62 a month and $408,142 of interest paid monthly. Pay $1,011.31 every two weeks instead and the loan clears in 628 payments — about 24 years 2 months — with $314,146 of interest. That is $93,997 saved and the mortgage gone roughly 5.9 years early, from a budgeting change many households barely feel because the drafts align with biweekly paydays.
Sources: Standard amortization simulated payment-by-payment at rate/26 per biweekly period; the comparison baseline is the same loan paid monthly. Last updated: October 2026.
Frequently asked questions
Is biweekly the same as paying twice a month?
No — and the difference is the whole point. Twice a month (semi-monthly) is 24 half-payments a year, exactly twelve monthly payments, so it saves almost nothing beyond a few days of interest timing. Biweekly is 26 half-payments: one full extra payment a year.
Why do servicer biweekly programs have a bad reputation?
Many do not apply your money when it arrives. They hold the first half-payment until the second arrives, remit monthly like before, and only forward the extra accumulated payment once a year — while charging a setup fee (often $300–$400) and monthly service fees. The interest benefit shrinks and the fees are certain. The CFPB has taken action against deceptive biweekly marketers; a free DIY extra payment to principal achieves the full effect.
Can I get the same result without changing my payment schedule?
Yes. Add 1/12 of a monthly payment to each monthly payment, marked "apply to principal", or make one extra full payment a year. The interest saved is essentially identical to true biweekly, and every servicer accepts it. Biweekly mainly helps households paid every two weeks who want the discipline automated.
Does biweekly help on a 15-year mortgage?
Yes, but less dramatically: the loan is already principal-heavy, so the extra payment cuts roughly 1–2 years and a smaller slice of interest. Run your numbers above — at 15-year rates the saving is real money, just not the six-figure headline of a 30-year loan at a high rate.
What formula does this biweekly mortgage calculator use?
Biweekly payment = monthly payment ÷ 2, collected 26 times a year (= 13 monthly payments). Each period: interest = balance × (annual rate ÷ 26); the rest reduces principal. The loan is re-amortized on a two-week clock. Because 26 half-payments exceed 24, one extra monthly payment a year reaches the principal; the simulation above simply steps the balance period by period until it reaches zero, which is why the payoff count (628 periods on the example loan) and the interest total are exact for the stated schedule. The worked example on this page applies the formula step by step with real numbers, so you can verify the result by hand.