Stamp Duty Calculator
Estimate transfer duty on a residential property purchase across all 8 Australian states and territories.
Mortgage Repayment Calculator
Loading…
How this mortgage calculator works
Repayments use the standard amortisation formula: PMT = P × r × (1+r)^n / ((1+r)^n − 1), where P is principal, r is the periodic interest rate, and n is the number of repayment periods. For a 30-year loan paid monthly, n = 360.
Fortnightly trick. Most Australian lenders accept 26 fortnightly payments per year, which is the equivalent of 13 monthly payments instead of 12. That single extra month each year shortens a 30-year loan by roughly 4-5 years and saves tens of thousands in interest.
Total interest is the sum of every repayment minus the original principal. Interest is heavily front-loaded — for the first ~7 years of a 30-year loan, most of each repayment goes to interest, not principal.
For ways to shorten the loan, see the lump-sum repayment calculator and the loan offset calculator.
Frequently asked questions
How is the repayment calculated?
Using the standard amortisation formula: PMT = P × r × (1+r)^n / ((1+r)^n − 1), where P is the loan principal, r is the periodic rate, and n is the number of repayment periods. The calculator divides the annual rate by the chosen repayment frequency (12, 26, or 52).
Are fortnightly repayments really cheaper than monthly?
Yes, slightly. Most banks accept 26 fortnightly payments per year (equivalent to 13 monthly payments rather than 12), so you make one extra monthly equivalent each year. Over a 30-year loan that can shorten the term by 4-5 years and save tens of thousands in interest. The calculator's fortnightly option models this correctly.
Should I use the comparison rate or the headline rate?
For pricing your repayments, use the headline rate (the actual rate charged on the loan). The comparison rate folds upfront, ongoing, and discharge fees into a single effective annual rate and is more useful for comparing two loans like-for-like. See the comparison-rate calculator for that.
What about offset accounts and extra repayments?
This calculator assumes scheduled repayments only. For modelling an offset balance or a lump-sum extra repayment, use the loan offset calculator or the lump-sum repayment calculator — both give the time and interest saved as separate figures.
Are these figures accurate for my actual loan?
Close, but check against your lender's amortisation schedule. Real loans can have monthly compounding of interest (slightly different from period-equivalent), introductory rates, fees added to repayments, and step-ups at year 1 or 5. The calculator gives the right ballpark for planning, not the exact figure that will appear on your statement.