Tool · Calculator
Mortgage Repayment Calculator
Calculate your home loan repayments and total interest by loan amount, interest rate, term, and repayment frequency. Australian dollars, principal-and-interest.
Enter your loan amount, interest rate, and term, then choose how often you repay and whether the loan is principal-and-interest or interest-only. The calculator shows your repayment per period, the total interest and amount repaid, and charts how your balance falls over the life of the loan.
Mortgage Repayment
Work out your repayment per period and the total interest you'll pay, with the option to model an interest-only period before the loan reverts to principal-and-interest.
Repayment per month
$3,635.97
Total interest
$708,949
Total repaid
$1,308,949
Hover or tap any year to see that year's principal and interest split.
This assumes a principal-and-interest loan with the rate held constant for the full term. Paying more frequently or making extra repayments reduces the interest you pay overall.
Estimates only - a clean principal-and-interest baseline I use to sanity-check repayments. It ignores fees, offset accounts, and rate changes, and it isn't financial advice.
Frequently asked questions
- How are mortgage repayments calculated?
- Repayments on a principal-and-interest loan use the standard amortisation formula. Each repayment covers the interest accrued for the period plus a slice of the principal. The periodic rate is the annual rate divided by the number of repayments per year, and the repayment is sized so the balance reaches zero at the end of the term.
- Does paying fortnightly instead of monthly save money?
- Often, yes. If you take the monthly repayment, halve it, and pay it every fortnight, you make the equivalent of 13 monthly repayments a year instead of 12. That extra repayment goes straight to principal, which can shave years and tens of thousands in interest off a 30-year loan.
- Why is the total interest so much higher than I expect?
- On a 30-year loan, interest compounds over a long horizon, so total interest can approach or exceed the amount you borrowed at typical rates. Lowering the rate, shortening the term, or making extra repayments all reduce the total interest substantially.
- What is an interest-only loan, and what happens after the interest-only period?
- On an interest-only loan your repayments cover only the interest for a set period, usually one to ten years, so the balance does not reduce. When that period ends the loan reverts to principal-and-interest, and the repayment is recalculated over the shorter remaining term. Because you delayed paying down principal, that later repayment is higher and the loan costs more interest overall. Switch the repayment type above to model this.
- Does this calculator include fees, offset accounts, or rate changes?
- No. It assumes a fixed rate for the full term and excludes establishment fees, ongoing fees, offset or redraw effects, and lenders mortgage insurance. Treat the result as a clean baseline, not a quote.