The minimum repayment looks manageable. That's the point. Lenders set it at the lowest level the system can sustain, and then they let compound interest do the rest of the work.
Most clients we sit down with have never run the calculation themselves. They know roughly what they pay each month, they know roughly what their balance is, and they have a vague sense that the loan will be paid off "eventually". Eventually, in most cases, means thirty years. And thirty years of interest on an Australian-sized mortgage is a number that tends to land hard when you finally see it written down.
What the minimum is actually doing
Take a $750,000 home loan at a 6.0% rate over 30 years. The minimum monthly repayment comes in at around $4,497. Over the full term you would pay $1,619,000 back to the lender. Of that, $869,000 is interest. You borrowed $750,000, and you handed back more than that in interest alone.
Most people are surprised by this number. The maths is simple but it lives in a world that nobody really visits. Banks aren't going to send you an annual statement that says "here's how much interest you owe us across the rest of the loan". Mortgage brokers focused on closing deals aren't paid to slow down and walk you through it either. So the figure stays hypothetical, and the minimum keeps coming out of the offset every month.
Why minimums favour the lender, not you
The way amortisation works is straight out of a textbook. In the early years of a 30-year loan, the bulk of every repayment is interest. Principal repayment ramps up slowly as the balance comes down. Run the numbers on the same $750,000 loan and you'll see that in year one, only around 22% of your repayments go to principal. The other 78% is interest.
That ratio doesn't flip until roughly year fourteen. For more than a decade, you are paying primarily for the privilege of holding the debt, not reducing it. The minimum repayment schedule is engineered to make this comfortable. Comfort, in this context, costs about $869,000.
The minimum repayment isn't a target. It's the floor the lender lets you sit on. Treating it as a target is what costs you decades and hundreds of thousands of dollars.
What changes when you push past the minimum
Here's where the maths starts working in your direction. Let's stay with the $750,000 example. If you add just $500 a month above the minimum (so $4,997 total), two things shift dramatically:
- Loan term drops by approximately 6 years, from 30 years to roughly 24.
- Total interest paid drops by approximately $186,000, from $869,000 down to about $683,000.
Six years off your mortgage. $186,000 you don't pay in interest. For an extra $500 a month you wouldn't really notice missing once you set it up.
If you can stretch to $1,000 above the minimum, the figures get sharper still. The loan is paid off in roughly 19.5 years, and the interest saving runs to around $300,000.
The offset account is the same conversation in reverse
Most strategic mortgages in Australia now sit alongside an offset account. Money in the offset reduces the loan balance interest is calculated on, day by day, without locking the cash away. If you keep $50,000 sitting in offset against that same $750,000 loan, you save somewhere in the order of $74,000 in interest over the life of the loan, and shave around 18 months off the term.
The cash is still yours. You can pull it back out tomorrow. The lender just stops charging you interest on the portion of your loan that's effectively covered by it. There are very few places where idle cash works that hard.
So why don't more people do this?
Three reasons turn up in conversation, again and again:
- Nobody walks them through the numbers. The maths is unglamorous and the lender has no incentive to put it in front of you.
- The savings feel abstract. $186,000 over 24 years doesn't trigger the same response as a $500 grocery bill today.
- Other priorities feel more urgent. Renovations, holidays, a newer car, school fees. The minimum repayment makes room for all of these to compete with the loan.
None of these are wrong. They're all rational responses to a system that has been carefully designed to make the minimum feel sufficient. The shift comes the moment you sit down and look at what the minimum actually costs over the life of the loan, and what a small extra contribution can do to that figure.
The takeaway
The minimum repayment is a starting line, not a finish line. It's the level at which the lender is happy. The level at which you should be happy is whatever number gets the loan paid off as quickly as your lifestyle reasonably allows, while keeping enough buffer in the offset to handle the unexpected.
That's not the same number for everyone. It depends on income, dependants, deductible vs non-deductible debt, where you are in your career, and what you're trying to do beyond the mortgage. But it's almost never the minimum.