Weekly vs Fortnightly vs Monthly Mortgage Repayments

Short answer

Changing a mortgage from monthly to a correctly recalculated fortnightly or weekly schedule usually produces only a small interest difference if the loan still runs for the same term.

The larger saving often quoted for fortnightly repayments comes from paying half the monthly repayment every two weeks. There are 26 fortnights in a year, so this method pays 13 monthly equivalents instead of 12. The saving comes mainly from the extra principal repaid, not from the word "fortnightly".

Use the Mortgage Repayment Calculator to compare equal-term weekly, fortnightly and monthly schedules. Use the Extra Repayments Calculator to model an amount above the scheduled repayment.

Two methods that should not be confused

1. Equal-term repayments

A lender or calculator can recalculate the scheduled repayment so the loan is paid off over the same term at the selected frequency.

For a $600,000 principal and interest loan at 6% over 30 years, this site's model estimates approximately:

The interest difference is modest because each schedule is designed to clear the same balance over 30 years. The model compounds interest at the selected repayment frequency and assumes the rate never changes.

2. Half the monthly amount every fortnight

Half of the $3,597.30 monthly repayment is about $1,798.65. Paying that every fortnight results in about $46,765 paid each year, compared with about $43,168 under 12 monthly repayments.

Under the same simplified assumptions, that larger fortnightly payment could clear the loan in roughly 24 years and 6 months, with total interest around $548,000. The result is materially lower because the borrower is paying about one extra monthly repayment each year.

Actual lender results can differ because of daily interest calculations, repayment rounding, payment dates, fees, rate changes and how the lender treats extra amounts.

What the calculator's frequency selector does

The frequency selector on the Mortgage Repayment Calculator calculates a fresh repayment for the chosen frequency over the full loan term.

It does not automatically divide the monthly repayment by two and treat the difference as an extra repayment. If that is the strategy you want to test, enter the higher payment in the Extra Repayments Calculator.

This distinction prevents a common comparison error: putting a 30-year monthly schedule beside a faster fortnightly schedule and attributing the entire saving to payment timing.

When repayment frequency can still help

A frequency that matches income can make budgeting easier. A fortnightly pay cycle may suit a fortnightly repayment because money leaves the account soon after salary arrives.

More frequent payments can also reduce the balance slightly earlier. The interest effect depends on when the lender credits the payment and how interest accrues. Many Australian home loans calculate interest daily, but loan contracts and repayment systems differ.

The practical questions to ask the lender are:

• Is the fortnightly amount a true recalculated repayment or half the monthly amount?
• Are amounts above the minimum treated as extra repayments?
• Is interest calculated daily and when is each payment credited?
• Are extra repayments capped on a fixed-rate loan?
• Can extra repayments be redrawn, and do fees or limits apply?
• Will the direct debit change automatically if the interest rate changes?

Common mistakes

• Assuming every fortnightly schedule creates a thirteenth monthly repayment.
• Comparing repayment amounts without converting them to an annual total.
• Treating a calculator's fixed-rate model as a lender quote.
• Ignoring fixed-loan extra repayment caps or break-cost conditions.
• Choosing a payment frequency that creates cash-flow stress between pay days.
• Counting redraw money as permanently available without checking the loan terms.

Sources

• ASIC Moneysmart: pay off your mortgage faster, including its explanation of half-monthly fortnightly payments. Checked 10 July 2026.
• ASIC Moneysmart: mortgage calculator, including calculation assumptions and limitations. Checked 10 July 2026.

General information disclaimer

This guide is general information only. It is not financial advice, credit advice, a repayment quote or a recommendation to change a loan. Results are indicative and based on the assumptions entered. Interest rates, lender calculations, fees and loan terms may vary. Check your contract and confirm any repayment change with the lender.