Blog · Mortgages

Switching to biweekly payments partway through a mortgage

28 August 2026 · 6 min read

Every biweekly calculator online assumes you start on day one. Almost nobody does — you hear about it in year four, or your pay changes to fortnightly in year seven. Here's what the switch is worth from where you actually are.

The numbers

A $400,000 mortgage at 6.5% over 30 years. Monthly payment $2,528.27, total interest $510,178 if you never change anything. Switching to half that payment every two weeks, at different points:

Two things worth taking from that. Switching in year five still captures 64% of what switching on day one would have — so if you're early-ish, you haven't missed much. And switching in year twenty captures 8%, at which point you're rearranging your bank transfers for very little.

Why it works, which is not what you're usually told

The common explanation is that paying fortnightly means interest compounds against a lower balance more often. That's technically true and almost entirely irrelevant — it accounts for a small fraction of the saving.

Which means biweekly isn't a clever financial instrument. It's an extra payment a year, arriving in a form that doesn't feel like a decision. On this loan, switching to biweekly in year five and adding about $211 a month in year five land within a few hundred dollars of each other over the life of the loan.

That's not an argument against it. For a lot of people the automatic version is the one that actually happens, and a plan you keep beats a better plan you abandon. But it does change what you should compare it against.

Check this before you call the lender

• Ask whether they apply each half-payment on arrival. Many servicers hold the first half in a suspense account until the second arrives, then apply one normal monthly payment. If they do that, you get the 13th-payment benefit but none of the fortnightly balance reduction — and some don't even give you that.
• Ask what it costs. Third-party "biweekly payment programs" charge setup fees and monthly fees to do something your servicer will usually do for free, or that you can replicate yourself for nothing.
• Ask whether it's reversible. If your income is irregular, committing to a payment every two weeks is a real constraint. Extra payments you choose month by month aren't.

The version with no phone call

If the answers above are unsatisfying, you can get the same result yourself: divide your monthly payment by twelve and add that to each month's payment, marked principal only. On this loan that's $210.69 a month. It produces one extra payment a year, applied directly to the balance, with no program to enrol in and nothing to unwind if your circumstances change.

The one thing to verify either way is that extra money is actually reaching the principal. Money sent without instruction is often applied to your next scheduled payment instead, where it sits and saves you nothing. Check the statement after the first one and confirm the balance dropped by what you sent.

So is it worth doing?

If you're in the first decade and your servicer applies payments as they arrive, yes — $44,525 to $117,496 on this loan is real money for a change in how you schedule a transfer. If you're past year fifteen, the honest answer is that the money is probably worth more somewhere else: a retirement match, higher-rate debt, or an emergency fund all beat a 6.5% guaranteed return.

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