Bi-Weekly Mortgage Payment Calculator
Compare bi-weekly vs monthly mortgage payments and see the interest and time you save by making 26 half-payments a year.
A bi-weekly mortgage calculator shows how much interest and time you save by paying half your monthly mortgage payment every two weeks instead of one full payment each month. The entire benefit comes from a calendar quirk: a year has 52 weeks, so 26 half-payments equal 13 full monthly payments rather than 12. That one extra payment a year goes entirely to principal, the balance that interest is charged on falls faster, and the loan finishes years early. Note that bi-weekly is not the same as twice-a-month: paying on the 1st and 15th is 24 half-payments a year — exactly 12 full payments — and produces no extra principal at all.
Enter your balance, rate, and term above, and the tool reports the bi-weekly payment amount, the interest saved, and the time cut from the loan compared with the standard monthly schedule.
How it's calculated
The monthly payment comes from the standard annuity formula:
Payment = P · r / (1 − (1 + r)−n)
where P is the balance, r the monthly rate
(annual rate ÷ 12), and n the number of payments. The
bi-weekly schedule is then modeled as paying an extra one-twelfth of the
monthly payment into principal each month — algebraically identical to 26
half-payments a year, and free of calendar drift. The calculator builds
both amortization schedules month by month, charging
balance × r in interest and applying the rest to principal,
and reports the difference. Full formulas are on our
methodology page, and the CFPB's explainer on
how paying down a mortgage works
covers the underlying interest-vs-principal split.
Worked example: $320,000 at 6.5% over 30 years
Take the calculator's default scenario: a $320,000 loan at 6.5% over 30 years. The monthly payment is $2,022.62, so the bi-weekly payment is $1,011.31, and the standard schedule costs $408,142 in total interest. Switching to bi-weekly payments cuts total interest to $315,069 — a saving of $93,073 — and pays the loan off in 24 years 2 months, 5 years 10 months early. Here is how the same switch behaves at other rates, computed with the same engine as the tool above:
| Rate ($320,000, 30 yr) | Monthly payment | Interest, monthly plan | Interest, bi-weekly | Interest saved | Time saved |
|---|---|---|---|---|---|
| 5.5% | $1,816.92 | $334,093 | $268,411 | $65,682 | 5 yr 1 mo |
| 6.5% | $2,022.62 | $408,142 | $315,069 | $93,073 | 5 yr 10 mo |
| 7.5% | $2,237.49 | $485,495 | $358,315 | $127,180 | 6 yr 8 mo |
The pattern is worth reading closely. Time saved depends on the rate and term, not the balance — a $200,000 loan and a $450,000 loan at 6.5% both finish 5 years 10 months early, while the dollar savings scale with size ($58,171 and $130,884 respectively). The higher the rate, the more the calendar trick is worth. Term matters too: on a 15-year loan at 6.5% the same switch saves only $24,763 and 1 year 10 months, because a shorter loan simply has less interest to remove. Enter your own numbers above for exact figures.
When should you use this calculator?
Use it before enrolling in any bi-weekly payment plan, to see the exact interest and time saving the schedule buys on your loan — and especially before paying for one. Banks and third-party services sell bi-weekly programs with setup or per-transaction fees, but the arithmetic above is free to replicate: divide your monthly payment by 12 and add that amount to each month's payment as extra principal. Run the tool, note the savings, and weigh any program fee against a benefit you can capture yourself at no cost. It is also useful for comparing acceleration strategies — the equivalent extra-per-month figure lets you line the bi-weekly plan up against a straightforward extra-payment plan of any size you like.
The calculator answers the mechanical question: what 13 payments a year instead of 12 does to this loan's interest and payoff date. Whether that money is better used elsewhere — higher-rate debt, savings, investing — is a judgment the tool leaves to you.
Assumptions and limitations
- The model applies one-twelfth of the monthly payment as extra principal each month — the standard, drift-free equivalent of a true bi-weekly schedule. Actual servicer crediting dates can shift figures slightly.
- Some servicers hold half-payments in suspense until the second half arrives rather than applying them on receipt. Confirm how yours credits partial payments; held payments still produce the 13th-payment effect but not the small mid-cycle benefit.
- The rate is fixed for the full term; adjustable-rate loans are not modeled.
- Escrow items (taxes, insurance, PMI) are excluded; payments here are principal and interest only.
- No prepayment penalty is modeled. Most conforming loans have none, but check your documents — the CFPB explains how prepayment penalties work.
- Third-party program fees are not modeled; subtract any fee from the reported savings when evaluating one.
This page is educational content about how bi-weekly payment schedules affect mortgage amortization. It is not financial advice and does not consider your personal circumstances. For decisions that matter, consult a qualified professional.
Last reviewed: 2026-07-09