How does a biweekly mortgage payment save interest?

A biweekly payment plan means you make a payment every two weeks, which adds up to 26 half-payments per year (the equivalent of 13 full monthly payments, rather than 12). That extra payment each year reduces your outstanding principal faster, which means less interest accumulates over time. On a typical 30-year mortgage, switching to biweekly payments can cut around 4 to 6 years off the loan term and save tens of thousands of dollars in interest.

What is the difference between biweekly and twice-monthly mortgage payments?

Biweekly payments are made every two weeks (26 payments per year), which results in 13 full monthly payments annually. Twice-monthly payments (semi-monthly) are made on fixed dates each month, such as the 1st and 15th, which equals exactly 24 half-payments or 12 full monthly payments per year. Only biweekly payments produce an extra payment each year, which is what accelerates payoff. Some lenders offer biweekly programs; others accept extra principal payments as an equivalent alternative.

Can I set up biweekly mortgage payments with my New Zealand bank?

New Zealand lenders typically offer weekly, fortnightly, and monthly repayment frequencies. Fortnightly payments work in the same way as biweekly payments: 26 payments per year equals 13 full monthly equivalents. Ask your lender to confirm that your repayment amount is calculated as half your monthly payment (not simply dividing by 26), so the extra payment effect applies. Alternatively, you can achieve the same result by making one extra voluntary lump-sum payment per year equal to your normal monthly repayment.

Biweekly Mortgage Calculator

See how making mortgage payments every two weeks instead of monthly reduces your loan term and saves interest. A biweekly plan produces 26 half-payments per year, equivalent to 13 full monthly payments instead of 12 - that one extra payment each year can shave years off your mortgage and save tens of thousands of dollars.

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Updated June 2026 Standard amortisation formula. Compatible with NZ fortnightly repayment schedules.

1. Your Mortgage Details

Loan amount

Annual interest rate % p.a.

Loan term

2. Biweekly Payment Method

Biweekly payment calculation

Extra lump sum per year (optional)

Your biweekly payment

Every two weeks (26 times per year)

Monthly vs Biweekly Comparison

Monthly Total Interest

Standard monthly schedule

Interest Saved
-
With biweekly payments

Years Saved

Earlier payoff date

Biweekly Payoff

Years to pay off loan

Monthly Repayment Schedule

Loan amount-

Annual interest rate-

Loan term-

Monthly payment-

Total payments-

Total interest paid-

Biweekly Repayment Schedule

Biweekly payment-

Extra annual payments-

Effective annual payments-

Payoff period-

Total paid-

Total interest paid-

Interest Rate Comparison at Different Rates

Interest Rate	Monthly Payment	Monthly Total Interest	Biweekly Total Interest	Interest Saved	Years Saved

Summary: Enter your loan details above to see your savings.

How Biweekly Mortgage Payments Work

The biweekly mortgage strategy is one of the simplest ways to pay off a home loan faster without refinancing or dramatically changing your budget. Instead of making one payment per month (12 per year), you make a payment every two weeks (26 per year). Since 26 half-payments equals 13 full monthly payments, you effectively make one extra full payment every year without it feeling like a large lump sum.

That extra payment goes directly to reducing your principal balance, which means less interest accrues over the remaining term. Because mortgage interest is calculated on the outstanding balance, every dollar you pay down early saves you interest in every subsequent period.

The Formula

The standard monthly mortgage payment uses the amortisation formula:

Monthly payment = P × [r(1+r)ⁿ] / [(1+r)ⁿ - 1]

Where P is the loan principal, r is the monthly interest rate (annual rate / 12), and n is the number of monthly payments (years × 12).

The biweekly payment is calculated as half the standard monthly payment. Over a year, you make 26 such payments (26 × half-payment = 13 full monthly equivalents). To model the payoff period, the remaining balance after each biweekly payment is recalculated using the biweekly interest rate (annual rate / 26).

Worked Example

Using the default inputs: a $600,000 loan at 6.5% per annum over 30 years.

Detail	Monthly Schedule	Biweekly Schedule
Payment amount	$3,792.41 per month	$1,896.20 every 2 weeks
Payments per year	12	26 (= 13 monthly equiv.)
Loan term	30 years	approximately 24.2 years (24 yrs 2 mths)
Total interest paid	approximately $765,267	approximately $589,023
Interest saved	-	approximately $176,244
Years saved	-	approximately 5.8 years

The exact figures from the calculator above match these defaults. Results will vary with different loan amounts, rates, or terms.

Biweekly vs Fortnightly in New Zealand

New Zealand lenders commonly offer fortnightly repayment, which works identically to biweekly: 26 payments per year. When setting up fortnightly payments with your bank, confirm that the payment amount is set to exactly half your monthly repayment amount. Some banks may default to dividing the annual repayment by 26, which produces a slightly different payment and a smaller interest saving. The half-monthly method is the standard biweekly approach and produces the larger saving shown in this calculator.

Other Ways to Pay Down Your Mortgage Faster

One extra payment per year: If your lender does not offer biweekly payments, making one additional voluntary payment equal to your monthly amount achieves roughly the same result.
Round up your payments: Rounding up to the nearest $100 or $500 reduces the principal slightly faster each period.
Lump sum payments: Putting tax refunds, bonuses, or inheritance funds directly onto your mortgage can have a significant impact because of the compounding interest effect.
Shorten your loan term: Refinancing to a shorter term (for example, from 30 to 20 years) forces faster paydown but raises the monthly commitment.

Related Calculators

Mortgage Calculators: all NZ mortgage tools in one place.
Mortgage Extra Repayment Calculator: see the effect of any extra regular payment.
Mortgage Repayment Frequency Calculator: compare weekly, fortnightly, and monthly schedules.
Mortgage Lump Sum Impact Calculator: model a one-off extra payment.
Mortgage Repayment Calculator: calculate your standard monthly repayment.

Sources and method: Standard mortgage amortisation formula (principal, interest, term). Biweekly savings modelled by iterating a balance reduction schedule at the biweekly rate (annual rate / 26) with 26 half-monthly payments per year. Consistent with methods described by the Consumer Financial Protection Bureau (CFPB) and ANZ, ASB, BNZ, Westpac NZ mortgage documentation.

This calculator provides indicative estimates only. Actual savings depend on your lender's exact calculation method, whether they apply payments immediately or at month-end, break fees, and any applicable loan conditions. Consult your lender or a registered financial adviser before making changes to your mortgage structure.