Guide
Fortnightly vs monthly mortgage repayments
Fortnightly vs monthly mortgage repayments is a comparison with a trick in it. Two different setups share the name fortnightly. On the reference loan they differ by more than $157,000. One is worth starting this week. The other is a rounding error wearing the same name.
The figures below are computed on a $600,000 principal and interest loan at 6.2% over 30 years, repaying about $3,675 a month, the same reference loan used across this site.
The version that works: half-payments
Take the monthly repayment, halve it, and pay that every fortnight. On the reference loan that is about $1,837. A year holds 26 fortnights, so this pays 26 halves. That is 13 full repayments instead of 12. One extra repayment a year lands on the principal, without ever feeling like extra.
Computed out, the loan is repaid in about 24 years and 5 months instead of 30, and total interest falls from $722,933 to $563,483. That is $159,450 saved by an arrangement most borrowers could set up in their banking app tonight.
The version that does not: true fortnightly
Some lenders convert the repayment the exact way: the monthly amount times 12, divided by 26. That pays the same total each year, just in smaller pieces. The only gain is that some money arrives a little earlier in each cycle.
Computed on the reference loan, this saves $1,833 over the full 30 years. Not per year. In total. Ask for fortnightly, receive this version, and you have changed your pay cycle and almost nothing else. The two versions differ by $157,617. The word on the statement is the same.
How to check which one you have
Multiply your fortnightly repayment by 26. Compare it with your old monthly repayment times 12. If the two match, you have the true version, and the benefit is near zero. If the fortnightly total is about one repayment larger, you have the half-payment version, and the extra is doing real work.
Setting it up yourself avoids the ambiguity. Halve the monthly figure, set the transfer, and the arithmetic takes care of the rest. The one caution is a fixed rate loan, where the extra month a year counts against the extra repayment cap.
Common questions
Is it better to pay my mortgage fortnightly or monthly?
Only if the fortnightly amount is half the monthly repayment. That produces 26 half-payments a year, which equals 13 monthly repayments instead of 12, and the extra one goes straight to principal. On a $600,000 loan at 6.2% it saves $159,450 and about five and a half years. A fortnightly amount calculated as the monthly repayment times 12 divided by 26 saves almost nothing.
How do I convert my monthly repayment to fortnightly?
Divide the monthly repayment by two and pay that every fortnight. On the reference loan that is about $1,837 a fortnight. Do the division yourself rather than accepting a converted figure, because a lender-calculated fortnightly amount is often the monthly repayment spread evenly across 26 payments, which removes the benefit.
Why does true fortnightly save almost nothing?
Because it pays the same annual total as monthly, just in smaller pieces. The only gain is that some money arrives slightly earlier in each cycle, which on the reference loan is worth $1,833 over 30 years. The half-payment method works for a different reason: it quietly pays one extra monthly repayment a year.
Is paying weekly even better than fortnightly?
Marginally, and for the same reason. Half-payments weekly (a quarter of the monthly amount, 52 times a year) produce the same one extra repayment annually, with money arriving slightly earlier again. The gain over half-payment fortnightly is small. The schedule that matches your pay cycle is usually the one that survives.
Can I pay fortnightly on a fixed rate loan?
Usually, but the half-payment method is an extra repayment in disguise, about one month extra a year, and fixed loans commonly cap extra repayments. On the reference loan the extra is roughly $3,675 a year, which sits inside a typical $10,000 cap. Confirm the cap with the lender before switching.
Related reading: paying off a mortgage faster in Australia puts this lever beside the other three, and lump sum mortgage payment covers the one that outranks it.
Last reviewed 2026-08-19.