15-Year vs 30-Year Mortgage: Which Is Better?

The choice between a shorter and a longer mortgage term comes down to a single tension: pay more each month and be done sooner, or pay less each month and carry the debt — and its interest — for longer. There's no universally right answer, but once you see the numbers side by side, the decision usually gets clearer.

The core trade-off

Take a $500,000 loan at 6.0% and compare a 15-year term against a 30-year one:

The 15-year loan costs about $1,221 more a month — a real squeeze on any budget. But it saves roughly $320,000 in interest and hands you a debt-free home fifteen years earlier. The 30-year loan more than doubles the interest bill in exchange for breathing room in the monthly budget. That's the whole trade in one table.

A note for Australian borrowers

In the United States a 15-year mortgage is a distinct product, often with a noticeably lower rate. In Australia the 30-year loan is the default and true 15-year products are rare — but you don't need one to get the same result. Choose a shorter term outright if the lender offers it, or take a standard 30-year loan and simply repay it at the 15-year rate using extra repayments. More on why that second route is often the smart one below.

When a shorter term makes sense

You can comfortably afford the higher repayment

The maths only helps if the payment fits. If the higher repayment still leaves you room to save, cover emergencies and live without white-knuckling every bill, the interest savings are hard to argue with — you're effectively earning a guaranteed return equal to your mortgage rate on every extra dollar.

You want certainty and an earlier finish line

A shorter term forces discipline. There's no temptation to skip the extra payment because the extra payment is the payment. If being mortgage-free before retirement matters to you, locking in a shorter term removes the question.

When a longer term makes sense

You value lower, more flexible repayments

Life is rarely a straight line. A lower required repayment gives you slack for a new baby, a career change, a rate rise or a stretch of single income. You can always pay more on a 30-year loan; you can't easily pay less on a 15-year one without refinancing.

You'd put the difference to better use

That $1,221 a month doesn't have to vanish into interest savings. Directed into superannuation or long-term investments, it might out-earn the interest you'd have saved — especially given super's tax advantages. This is the "invest the difference" argument, and over long horizons it can win. The catch is that it only works if you actually invest the difference every month rather than absorbing it into lifestyle. See how that compounds with the compound interest calculator.

The option that often beats both

For many borrowers the best answer is a 30-year loan that you treat like a 15-year one. Take the lower required repayment as your safety net, then voluntarily pay the higher amount — or park spare cash in an offset account. You capture most of the interest savings while keeping the escape hatch: in a tight month you can drop back to the minimum without asking anyone's permission. You give up a little discipline and, in the US context, a slightly lower headline rate — but you buy flexibility that a locked-in short term can't offer.

Key takeaways

• A shorter term means higher repayments but dramatically less interest — around $320,000 less on a $500,000 loan at 6%.
• A longer term keeps monthly repayments low and flexible, at the cost of far more interest over time.
• In Australia you can mimic a 15-year loan with a 30-year one plus extra repayments or an offset account — often the most flexible choice.
• The "invest the difference" strategy only pays off if you genuinely invest it, every month.

Model both terms — and the effect of extra repayments — with the mortgage calculator, and pressure-test the repayment against your budget using the home affordability calculator.

The interest rate above is an illustrative example. Compare current rates and product features before choosing a loan.