Loan Repayment Calculator

A loan repayment calculator answers the most practical question in home buying: what will this actually cost me each month? By entering your loan amount, interest rate and loan term, you get an instant estimate of your repayment, the figure that has to sit comfortably inside your household budget for the next 25 or 30 years.

The maths behind it is the standard amortisation formula, where each repayment covers the interest accrued that period plus a slice of the principal. In the early years of a typical 30-year loan, most of each repayment goes to interest and only a little to principal; as the balance falls, that ratio steadily flips. This is why paying even a little extra early in the loan has an outsized effect on the total interest you pay.

Three inputs drive everything. The loan amount is your purchase price minus your deposit. The interest rate is the single biggest lever. On a $600,000 loan, a difference of just 0.5% p.a. changes your repayment by roughly $180 a month and tens of thousands over the life of the loan. The term trades monthly affordability against lifetime cost: a longer term lowers each repayment but increases total interest, while a shorter term does the reverse.

It is also worth deciding between principal-and-interest and interest-only repayments. Principal-and-interest is the default for owner-occupiers and steadily reduces what you owe. Interest-only keeps repayments lower for a set period but the balance does not fall, so it is generally used strategically by investors rather than as a way to afford a bigger home.

Our calculator lets you flex each input and see the repayment update instantly, so you can stress-test how your budget would cope at a higher rate before you commit. Remember these figures are indicative and exclude fees, offset benefits and rate changes. To see repayments alongside stamp duty, LMI and your full upfront costs, use our all-in-one calculator, and a Greystone broker can then confirm the exact repayment on a real product suited to you.